remove REV from integration test task definitions

This might be the most hacky thing we're doing here so far, but it's necessary for translations integration tests, where cached ancestor tasks will have a `REV` that doesn't match the `REF`, leading to errors such as:
```
[vcs 2024-12-20T16:35:08.992Z] executing ['git', 'config', '--global', '--add', 'safe.directory', '/builds/worker/checkouts/vcs']
[vcs 2024-12-20T16:35:08.994Z] executing ['git', 'clone', 'https://github.com/mozilla-releng/staging-firefox-translations-training', '/builds/worker/checkouts/vcs']
[vcs 2024-12-20T16:35:08.995Z] Cloning into '/builds/worker/checkouts/vcs'...
[vcs 2024-12-20T16:35:10.747Z] executing ['git', 'fetch', '--tags', '--force', 'https://github.com/mozilla-releng/staging-firefox-translations-training', 'refs/heads/main']
[vcs 2024-12-20T16:35:10.949Z] From https://github.com/mozilla-releng/staging-firefox-translations-training
[vcs 2024-12-20T16:35:10.949Z]  * branch            main       -> FETCH_HEAD
[vcs 2024-12-20T16:35:10.955Z] executing ['git', 'fetch', '--no-tags', 'https://github.com/mozilla-releng/staging-firefox-translations-training', 'refs/heads/main']
[vcs 2024-12-20T16:35:11.128Z] From https://github.com/mozilla-releng/staging-firefox-translations-training
[vcs 2024-12-20T16:35:11.128Z]  * branch            main       -> FETCH_HEAD
[vcs 2024-12-20T16:35:11.133Z] executing ['git', 'checkout', '-f', '-B', 'refs/heads/main', '876ad1a2de046271a45c979551c8650e5e1b75a2']
[vcs 2024-12-20T16:35:11.135Z] fatal: reference is not a tree: 876ad1a2de046271a45c979551c8650e5e1b75a2
```

Removing the `REV` will cause the `REF` to be used without issues:
```
[vcs 2024-12-20T18:15:48.936Z] executing ['git', 'config', '--global', '--add', 'safe.directory', '/builds/worker/checkouts/vcs']
[vcs 2024-12-20T18:15:48.938Z] executing ['git', 'clone', 'https://github.com/mozilla-releng/staging-firefox-translations-training', '/builds/worker/checkouts/vcs']
[vcs 2024-12-20T18:15:48.939Z] Cloning into '/builds/worker/checkouts/vcs'...
[vcs 2024-12-20T18:15:50.544Z] executing ['git', 'fetch', '--tags', '--force', 'https://github.com/mozilla-releng/staging-firefox-translations-training', 'refs/heads/main']
[vcs 2024-12-20T18:15:50.758Z] From https://github.com/mozilla-releng/staging-firefox-translations-training
[vcs 2024-12-20T18:15:50.758Z]  * branch            main       -> FETCH_HEAD
[vcs 2024-12-20T18:15:50.763Z] executing ['git', 'fetch', '--no-tags', 'https://github.com/mozilla-releng/staging-firefox-translations-training', 'refs/heads/main']
[vcs 2024-12-20T18:15:50.926Z] From https://github.com/mozilla-releng/staging-firefox-translations-training
[vcs 2024-12-20T18:15:50.926Z]  * branch            main       -> FETCH_HEAD
[vcs 2024-12-20T18:15:50.931Z] executing ['git', 'checkout', '-f', '-B', 'refs/heads/main', 'FETCH_HEAD']
[vcs 2024-12-20T18:15:51.929Z] Switched to a new branch 'refs/heads/main'
```

taskcluster/fxci_config_taskgraph/util/integration.py

@@ -101,6 +101,20 @@ def _rewrite_task_datestamps(task_def):
     return task_def
 
 
+def _remove_task_revisions(task_def):
+    """Rewrite revisions in task payloads to ensure that tasks do not refer to
+    out of date revisions."""
+    to_remove = set()
+    for k in task_def.get("payload", {}).get("env", {}):
+        if k.endswith("_REV"):
+            to_remove.add(k)
+
+    for k in to_remove:
+        del task_def["payload"]["env"][k]
+
+    return task_def
+
+
 def find_tasks(
     decision_index_path: str,
     include_attrs: dict[str, list[str]],
@@ -153,6 +167,11 @@ def find_tasks(
                     # All datestamps come in as absolute ones, many of which
                     # will be in the past. We need to rewrite these to relative
                     # ones to make the task reschedulable.
-                    tasks[upstream_task_id] = _rewrite_task_datestamps(task_def)
+                    # We also need to remove absolute revisions from payloads
+                    # to avoid issues with revisions not matching the refs
+                    # that are given.
+                    tasks[upstream_task_id] = _remove_task_revisions(
+                        _rewrite_task_datestamps(task_def)
+                    )
 
     return tasks