Adjust k6 test suite conditions

.github/workflows/k6-tests.yaml

@@ -1,5 +1,17 @@
 name: Run k6 Test Suite
-on: [push]
+on:
+  push:
+    paths:
+      - 'scripts/**'
+      - 'k6/**'
+  release:
+    types:
+      - created
+
+# Important: The k6 test suite will only be run against the latest
+# release of the Quickpizza service, not against the code in the
+# commit itself. Therefore, we only run this Action when the test
+# files themselves are modified (or on a new release).
 
 jobs:
   runner-job: