Add a changelog fragment for the Flow parser cleanup

The changelog check requires a fragment; this one records the internal
change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kbf3gLDo8mBJKpNE25WAwT
Signed-off-by: Christoph Knittel <ck@cca.io>

Author: cknitt

changes/prune-flow-parser.internal.md

@@ -0,0 +1 @@
+- Remove dead code from the vendored Flow parser, which is no longer synced with upstream, and include it in `make dead-code`.