fix: remove Python 3.7 from buildpack integration tests

Google Cloud Buildpacks dropped Python 3.7 support for Ubuntu 22.04.
The version is not available in their runtime manifest.

Note: Functions Framework still supports Python 3.7, which is tested
in unit and conformance tests using GitHub Actions with Ubuntu 20.04.

Author: taeold

.github/workflows/buildpack-integration-test.yml

@@ -14,17 +14,6 @@ on:
 permissions: read-all
 
 jobs:
-  python37:
-    uses: GoogleCloudPlatform/functions-framework-conformance/.github/workflows/buildpack-integration-test.yml@main
-    with:
-      http-builder-source: 'tests/conformance'
-      http-builder-target: 'write_http_declarative'
-      cloudevent-builder-source: 'tests/conformance'
-      cloudevent-builder-target: 'write_cloud_event_declarative'
-      prerun: 'tests/conformance/prerun.sh ${{ github.sha }}'
-      builder-runtime: 'python37'
-      builder-runtime-version: '3.7'
-      start-delay: 5
   python38:
     uses: GoogleCloudPlatform/functions-framework-conformance/.github/workflows/buildpack-integration-test.yml@main
     with: