Don't run periodic PR dependency checks on forks

As we do with the Flake Finder and other periodic jobs, skip the checks
for PR dependencies on forks.

Signed-off-by: Daniel Farrell <dfarrell@redhat.com>

.github/workflows/dependent-issues.yml

@@ -22,6 +22,7 @@ on:
 jobs:
   check:
     name: Check Dependencies
+    if: github.repository_owner == 'submariner-io'
     runs-on: ubuntu-latest
     steps:
       - uses: z0al/dependent-issues@70a1b2d4ee1cdc743af33498bd0204123953a887
@@ -35,4 +36,4 @@ jobs:
           check_issues: on
 
           # A comma-separated list of keywords to mark dependency.
-          keywords: depends on, Depends on
+          keywords: depends on, Depends on