ci: run the Scorecards action in PRs only on config update

Also, unify the string quotation a bit and drop one unnecessary
expression syntax (as everything in `if` statements is automatically
evaluated as an expression).

.github/workflows/scorecards.yml

@@ -8,9 +8,13 @@ on:
   schedule:
     - cron: '15 21 * * 6'
   push:
-    branches: [ "main" ]
+    branches:
+      - main
   pull_request:
-    branches: [ "main" ]
+    branches:
+      - main
+    paths:
+      - '.github/workflows/scorecards.yml'
 
 # Declare default permissions as read only.
 permissions: read-all
@@ -27,12 +31,12 @@ jobs:
       id-token: write
 
     steps:
-      - name: "Checkout code"
+      - name: Checkout code
         uses: actions/checkout@a12a3943b4bdde767164f792f33f40b04645d846 # tag=v3.0.0
         with:
           persist-credentials: false
 
-      - name: "Run analysis"
+      - name: Run analysis
         uses: ossf/scorecard-action@e363bfca00e752f91de7b7d2a77340e2e523cb18 # tag=v2.0.4
         with:
           results_file: results.sarif
@@ -51,7 +55,7 @@ jobs:
 
       # Upload the results as artifacts (optional). Commenting out will disable uploads of run results in SARIF
       # format to the repository Actions tab.
-      - name: "Upload artifact"
+      - name: Upload artifact
         uses: actions/upload-artifact@6673cd052c4cd6fcf4b4e6e60ea986c889389535 # tag=v3.0.0
         with:
           name: SARIF file
@@ -59,8 +63,8 @@ jobs:
           retention-days: 5
 
       # Upload the results to GitHub's code scanning dashboard.
-      - name: "Upload to code-scanning"
-        if: ${{ github.event_name != 'pull_request' }}
+      - name: Upload to code-scanning
+        if: github.event_name != 'pull_request'
         uses: github/codeql-action/upload-sarif@5f532563584d71fdef14ee64d17bafb34f751ce5 # tag=v1.0.26
         with:
           sarif_file: results.sarif