Prevent execution of spurious clean-up step, which then crashes.

The clean-up step for setting up Python and pip assumes that you do at least something with those programs -- and so that cache folders have been made, that need to be cleaned up. If nothing happens, the clean-up step then crashes on the non-existant cache folder.

.github/workflows/printer-linter-format.yml

@@ -19,6 +19,7 @@ jobs:
                 uses: actions/checkout@v3
 
             -   name: Setup Python and pip
+                if: env.GIT_DIFF && !env.MATCHED_FILES  # If nothing happens with python and/or pip after, the clean-up crashes.
                 uses: actions/setup-python@v4
                 with:
                     python-version: 3.11.x

.github/workflows/printer-linter-pr-diagnose.yml

@@ -17,6 +17,7 @@ jobs:
           fetch-depth: 2
 
       - name: Setup Python and pip
+        if: env.GIT_DIFF && !env.MATCHED_FILES  # If nothing happens with python and/or pip after, the clean-up crashes.
         uses: actions/setup-python@v4
         with:
           python-version: 3.11.x