Bump chex from 0.1.87 to 0.1.88

Bumps [chex](https://github.com/deepmind/chex) from 0.1.87 to 0.1.88.
- [Release notes](https://github.com/deepmind/chex/releases)
- [Commits](google-deepmind/chex@v0.1.87...v0.1.88)

---
updated-dependencies:
- dependency-name: chex
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -260,9 +260,9 @@ charset-normalizer==3.4.0 \
     --hash=sha256:fe9f97feb71aa9896b81973a7bbada8c49501dc73e58a10fcef6663af95e5079 \
     --hash=sha256:ffc519621dce0c767e96b9c53f09c5d215578e10b02c285809f76509a3931482
     # via requests
-chex==0.1.87 \
-    --hash=sha256:0096d89cc8d898bb521ef4bfbf5c24549022b0e5b301f529ab57238896fe6c5d \
-    --hash=sha256:ce536475661fd96d21be0c1728ecdbedd03f8ff950c662dfc338c92ea782cb16
+chex==0.1.88 \
+    --hash=sha256:234b61a5baa8132802e4b9c5657167d6c8a911d90a59a0bec47d537567e41b75 \
+    --hash=sha256:565de897b1373232cdfca5e699f50fa49403d2c7d23f6c5a75a97ef713d2fe36
     # via dm-meltingpot (setup.py)
 click==8.1.7 \
     --hash=sha256:ae74fb96c20a0277a1d615f1e4d73c8414f5a98db8b799a7931d1582f3390c28 \