ci: add pip exclusion for pyproject test fixtures (#483)

The dependabot config only had a uv ecosystem exclusion for the
pyproject/ test fixtures directory, not pip. Poetry-based fixtures
without uv.lock were picked up by the pip scanner, causing PR #481.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: ruromero

.github/dependabot.yml

@@ -52,6 +52,7 @@ updates:
   - package-ecosystem: "pip"
     directories:
       - "/test/providers/tst_manifests/pip/**"
+      - "/test/providers/tst_manifests/pyproject/**"
     schedule:
       interval: "monthly"
     labels: []