CI: Add path filters to python-deps workflow

No need to run this workflow on all PRs, only those that
change the Python dependency installation mechanism.

.github/workflows/python-deps.yml

@@ -7,6 +7,13 @@ on:
     # Run checks on reopened draft PRs to support triggering PR checks on draft PRs that were opened
     # by other workflows.
     types: [opened, synchronize, reopened, ready_for_review]
+    paths:
+      # Changes to this workflow.
+      - '.github/workflows/python-deps.yml'
+      # Changes to the Python package installation scripts and their tests.
+      - 'python-setup/**'
+      # Changes to the default CodeQL bundle version.
+      - '**/defaults.json'
 
 jobs:
   test-setup-python-scripts: