Update benchmark_pr.yml

Co-Authored-By: Mosè Giordano <765740+giordano@users.noreply.github.com>

Author: christiangnrd

.github/workflows/benchmark_pr.yml

@@ -8,7 +8,7 @@ permissions:
 
 jobs:
     generate_plots:
-        if: github.event.pull_request.head.repo.full_name == github.repository
+        if: "! github.event.pull_request.head.repo.fork"
         runs-on: ubuntu-latest
 
         steps: