chore: remove prerelease and core_deps from GHA (#17291)

Remove `prerelease` and `core_deps_from_source` tests from running in
GHA as part of presubmits. These tests will now be run as part of a
continuous Kokoro job instead.

Fixes #17243

Author: ohmayr

.github/workflows/unittest.yml

@@ -48,71 +48,6 @@ jobs:
       with:
         name: coverage-artifact-${{ '{{' }} matrix.python {{ '}}' }}
         path: .coverage-${{ matrix.python }}
-  unit-prerelease:
-    name: ${{ matrix.option }}
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        python: ["3.14"]
-        option: ["prerelease"]
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v4
-      # Use a fetch-depth of 2 to avoid error `fatal: origin/main...HEAD: no merge base`
-      # See https://github.com/googleapis/google-cloud-python/issues/12013
-      # and https://github.com/actions/checkout#checkout-head.
-      with:
-        fetch-depth: 2
-    - name: Setup Python
-      uses: actions/setup-python@v5
-      with:
-        python-version: ${{ matrix.python }}
-        allow-prereleases: true
-    - name: Install nox
-      run: |
-        python -m pip install --upgrade setuptools pip wheel
-        python -m pip install nox
-    - name: Run ${{ matrix.option }} tests
-      env:
-        BUILD_TYPE: presubmit
-        TARGET_BRANCH: ${{ github.base_ref || github.event.merge_group.base_ref }}
-        TEST_TYPE: ${{ matrix.option }}
-        # TODO(https://github.com/googleapis/google-cloud-python/issues/13775): Specify `PY_VERSION` rather than relying on the default python version of the nox session.
-        PY_VERSION: "unused"
-      run: |
-        ci/run_conditional_tests.sh
-  unit-core-deps-from-source:
-    name: ${{ matrix.option }}
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        python: ["3.14"]
-        option: ["core_deps_from_source-3.14"]
-    steps:
-    - name: Checkout
-      uses: actions/checkout@v4
-      # Use a fetch-depth of 2 to avoid error `fatal: origin/main...HEAD: no merge base`
-      # See https://github.com/googleapis/google-cloud-python/issues/12013
-      # and https://github.com/actions/checkout#checkout-head.
-      with:
-        fetch-depth: 2
-    - name: Setup Python
-      uses: actions/setup-python@v5
-      with:
-        python-version: ${{ matrix.python }}
-    - name: Install nox
-      run: |
-        python -m pip install --upgrade setuptools pip wheel
-        python -m pip install nox
-    - name: Run ${{ matrix.option }} tests
-      env:
-        BUILD_TYPE: presubmit
-        TARGET_BRANCH: ${{ github.base_ref || github.event.merge_group.base_ref }}
-        TEST_TYPE: ${{ matrix.option }}
-        # TODO(https://github.com/googleapis/google-cloud-python/issues/13775): Specify `PY_VERSION` rather than relying on the default python version of the nox session.
-        PY_VERSION: "unused"
-      run: |
-        ci/run_conditional_tests.sh
 
   cover:
     runs-on: ubuntu-latest