build: harden benchmark.yml permissions

Signed-off-by: Alex <[email protected]>

Author: sashashura

.github/workflows/benchmark.yml

@@ -8,6 +8,9 @@ on:
   pull_request: {}
   workflow_dispatch: {}
 
+permissions:
+  contents: read # to fetch code (actions/checkout)
+
 jobs:
   federation-benchmark:
     name: Federation Benchmark with ${{matrix.products_size}} Products