workflows: only run conflicts and update flake on main repo (#6893)

.github/workflows/conflicts.yml

@@ -5,6 +5,7 @@ on:
 jobs:
   triage:
     runs-on: ubuntu-latest
+    if: github.repository_owner == 'nix-community'
     steps:
       - uses: mschilde/auto-label-merge-conflicts@master
         with:

.github/workflows/update-flake.yml

@@ -8,6 +8,7 @@ on:
 jobs:
   update:
     runs-on: ubuntu-latest
+    if: github.event_name != 'schedule' || github.repository_owner == 'nix-community'
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4