[CI] Don't run benchmarks on PRs from forks

Author: giordano

.github/workflows/benchmark_aggregate.yml

@@ -14,7 +14,7 @@ on:
 
 jobs:
   benchmark:
-    if: ${{ !contains(github.event.head_commit.message, '[skip benchmarks]') }}
+    if: ${{ !contains(github.event.head_commit.message, '[skip benchmarks]') && ! github.event.pull_request.head.repo.fork }}
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4