NIFI-9608 Disabled system-tests workflow for pull requests

This closes #5689

Signed-off-by: David Handermann <exceptionfactory@apache.org>

.github/workflows/system-tests.yml

@@ -19,14 +19,6 @@ on:
   # Run every day at 00:00
   schedule:
     - cron: "0 0 * * *"
-  # Run on pull requests for selected modules
-  pull_request:
-    paths:
-      - 'nifi-api/**'
-      - 'nifi-framework-api/**'
-      - 'nifi-nar-bundles/nifi-framework-bundle/**'
-      - 'nifi-system-tests/**'
-      - 'nifi-stateless/**'
 
 env:
   DEFAULT_MAVEN_OPTS: >-