[CI] Benchmark upload broken after action link hardening

Author: esigo

.github/workflows/benchmark.yml

@@ -1,6 +1,6 @@
 name: OpenTelemetry-cpp benchmarks
 on:
-  push:
+  pull_request:
     branches:
       - main
 
@@ -48,7 +48,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
-      - uses: actions/download-artifact@2a5974104b6d5dbdb2f9468a3e54da3bdd241578 # v4.2.1
+      - uses: actions/download-artifact@95815c38cf2ff2164869cbab79da8d1f422bc89e # main March 2025
         with:
           name: benchmark_results
           path: benchmarks