chore: remove unused API keys from CI workflow

Remove STACKONE_API_KEY and OPENAI_API_KEY environment variables from CI workflow as they are not used in tests:
- STACKONE_API_KEY is only used in a skipped integration test
- OPENAI_API_KEY is not used in any tests

Author: ryoppippi

.github/workflows/ci.yaml

@@ -40,9 +40,6 @@ jobs:
             sync-extras: "--all-extras"
           - python-version: "3.13"
             sync-extras: "--all-extras"
-    env:
-      STACKONE_API_KEY: ${{ secrets.STACKONE_API_KEY }}
-      OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
     steps:
       - name: Checkout repository
         uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
@@ -67,9 +64,6 @@ jobs:
   coverage:
     runs-on: ubuntu-latest
     if: github.ref == 'refs/heads/main'
-    env:
-      STACKONE_API_KEY: ${{ secrets.STACKONE_API_KEY }}
-      OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
     steps:
       - name: Checkout repository
         uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1