Revert version to v0.8.1

The version number was mistakenly updated to v0.9.0. This change reverts it to the correct version, v0.8.1, to maintain consistency with the current release cycle and ensure proper version tracking. No functional changes accompany this reversion.

Author: csgoh

src/processpiper/version.py

@@ -21,4 +21,4 @@
 # SOFTWARE.
 
 """Version information for processpiper."""
-__version__ = "v0.9.0"
+__version__ = "v0.8.1"