CI: git checkout speed tweaks in linting jobs. (#50169)

.github/workflows/ci.yml

@@ -90,7 +90,8 @@ jobs:
       - uses: 'actions/checkout@v4'
         name: 'Checkout'
         with:
-          fetch-depth: 0
+          # the WooCommerce plugin package uses phpcs-changed for linting, which requires non-shallow git-history.
+          fetch-depth: ${{ ( ( matrix.projectName == '@woocommerce/plugin-woocommerce' && '0' ) || '1' ) }}
 
       - uses: './.github/actions/setup-woocommerce-monorepo'
         name: 'Setup Monorepo'