Prepare for 0.8.1 release (#1507)

This change increments the version number and adds a prelude for the
0.8.1 release notes.

docs/conf.py

@@ -38,7 +38,7 @@
 version = os.getenv("VERSION_STRING", "0.8")
 
 # The full version, including alpha/beta/rc tags
-release = os.getenv("RELEASE_STRING", "0.8.0")
+release = os.getenv("RELEASE_STRING", "0.8.1")
 
 project = "Qiskit Experiments"
 copyright = f"2021-{datetime.date.today().year}, Qiskit Development Team"  # pylint: disable=redefined-builtin

qiskit_experiments/VERSION.txt

@@ -1 +1 @@
-0.8.0
+0.8.1

releasenotes/notes/prelude-0.8.1-d98e520584b5d73e.yaml

@@ -0,0 +1,8 @@
+---
+prelude: >
+    Qiskit Experiments 0.8.1 is a minor update to 0.8.0 to improve
+    compatibility with dependencies Qiskit and CVXPY. References to code in
+    these dependencies were updated to avoid triggering deprecation warnings, so
+    that the code will continue to work as new versions of Qiskit and CVXPY are
+    released. Additional examples were added to the documentation, and some
+    typos were corrected.

releasenotes/notes/qiskit13-deprecations-afece0ceea29f3f7.yaml

@@ -3,4 +3,5 @@ upgrade:
   - |
     Minor adjustments were made to Qiskit Experiments internals to avoid
     deprecation warnings when using Qiskit 1.3. See `#1482
-    <https://github.com/qiskit-community/qiskit-experiments/pull/1482>`__.
+    <https://github.com/qiskit-community/qiskit-experiments/pull/1482>`__ and
+    `#1491 <https://github.com/qiskit-community/qiskit-experiments/pull/1491>`__.