chore(ci): remove unneeded permissions from system-tests subworkflow

Author: nccatoni

.github/workflows/system-tests.yml

@@ -48,9 +48,7 @@ jobs:
       TEST_OPTIMIZATION_API_KEY: ${{ secrets.DD_API_KEY_CI_APP }}
       DD_API_KEY: ${{ secrets.DD_API_KEY_CI_APP }}
     permissions:
-      contents: read
       id-token: write
-      packages: write
     with:
       library: cpp_httpd
       binaries_artifact: system_tests_binaries