chore: remove support for Python 3.7 and 3.8

Author: vchudnov-g

.github/workflows/unittest.yml

@@ -8,27 +8,18 @@ on:
 jobs:
   run-unittests:
     name: unit${{ matrix.option }}-${{ matrix.python }}
-    # TODO(https://github.com/googleapis/gapic-generator-python/issues/2303): use `ubuntu-latest` once this bug is fixed.
-    # Use ubuntu-22.04 until Python 3.7 is removed from the test matrix
-    # https://docs.github.com/en/actions/using-github-hosted-runners/using-github-hosted-runners/about-github-hosted-runners#standard-github-hosted-runners-for-public-repositories
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         option: ["", "_grpc_gcp", "_wo_grpc", "_w_prerelease_deps", "_w_async_rest_extra"]
         python:
-          - "3.7"
-          - "3.8"
           - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"
           - "3.13"
           - "3.14"
         exclude:
-          - option: "_wo_grpc"
-            python: 3.7
-          - option: "_wo_grpc"
-            python: 3.8
           - option: "_wo_grpc"
             python: 3.9
     steps: