build: avoid run find inactive authors on forked repo

PR-URL: #40465
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

.github/workflows/find-inactive-collaborators.yml

@@ -13,7 +13,7 @@ env:
 
 jobs:
   find:
-
+    if: github.repository == 'nodejs/node'
     runs-on: ubuntu-latest
 
     steps: