Fix grep pattern for exact branch name matching

Co-authored-by: FlywithYou1 <137418305+FlywithYou1@users.noreply.github.com>

Author: Copilot

.github/workflows/build-vsix.yml

@@ -93,7 +93,7 @@ jobs:
           
           # Create or checkout release branch
           git fetch origin
-          if git ls-remote --heads origin | grep -q '^refs/heads/release$'; then
+          if git ls-remote --heads origin | grep -q 'refs/heads/release$'; then
             git checkout -b release origin/release
           else
             git checkout --orphan release