ci: Let github runner run only in the prometheus-operator main repository

.github/workflows/e2e-prometheus3.yaml

@@ -9,6 +9,7 @@ jobs:
   e2e-tests:
     name: E2E experimental version tests
     runs-on: ubuntu-latest
+    if: ${{ github.repository == 'prometheus-operator/prometheus-operator' }}
     strategy:
       # since upgrade test was failing other tests were cancelled, setting this so that other test run
       fail-fast: false
@@ -76,6 +77,7 @@ jobs:
     needs:
       - e2e-tests
     runs-on: ubuntu-latest
+    if: ${{ github.repository == 'prometheus-operator/prometheus-operator' }}
     steps:
       - name: Mark the job as a success
         if: needs.e2e-tests.result == 'success'

.github/workflows/stale.yaml

@@ -6,6 +6,7 @@ on:
 jobs:
   stale:
     runs-on: ubuntu-latest
+    if: ${{ github.repository == 'prometheus-operator/prometheus-operator' }}
     steps:
       - uses: actions/stale@v9
         with:

.github/workflows/test-prom-version-upgrade.yaml

@@ -8,6 +8,7 @@ jobs:
   upgrade-prometheus:
     name: Upgrade Prometheus
     runs-on: ubuntu-latest
+    if: ${{ github.repository == 'prometheus-operator/prometheus-operator' }}
     steps:
     - name: Reclaim disk space
       run: |