Only run scheduled jobs on upstream (#145)

.github/workflows/get-python-versions.yml

@@ -12,6 +12,7 @@ defaults:
 
 jobs:
   find_new_versions:
+    if: github.repository_owner == 'actions'
     name: Find new versions
     runs-on: ubuntu-latest
     outputs:

.github/workflows/validate-manifest.yml

@@ -19,6 +19,7 @@ defaults:
 
 jobs:
   validation:
+    if: github.repository_owner == 'actions'
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2