chore(ci): use dd-sts for system-tests test optimization (#788)

* chore(ci): use dd-sts for system-tests test optimization

* chore(ci): remove dd_sts_policy from system-tests subworkflow

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

* chore(ci): pin system-tests workflow to 1e5d6b709

* Remove API key

* fix: add contents:read permission to system-tests workflow call

* chore(ci): pass ref to system-tests reusable workflow

Author: nccatoni

.github/workflows/system_tests.yml

@@ -28,15 +28,13 @@ jobs:
   system-tests:
     needs:
       - build
-    uses: DataDog/system-tests/.github/workflows/system-tests.yml@main
-    secrets:
-      DD_API_KEY: ${{ secrets.DD_API_KEY }}
-      TEST_OPTIMIZATION_API_KEY: ${{ secrets.TEST_OPTIMIZATION_API_KEY }}
+    uses: DataDog/system-tests/.github/workflows/system-tests.yml@1e5d6b7096279ca43ce4826fda3cc805635b63c1
     permissions:
       contents: read
-      packages: write
+      id-token: write
     with:
       library: python_lambda
+      ref: 1e5d6b7096279ca43ce4826fda3cc805635b63c1
       binaries_artifact: binaries
       scenarios_groups: tracer_release
       skip_empty_scenarios: true