Update dependencies on actions/checkout and actions/cache.

The new versions use Node.js 16 (eliminating warnings about Node.js 12
deprecation).

.github/workflows/tests.yml

@@ -38,7 +38,7 @@ jobs:
     env:
       TZINFO_GEM: ${{ matrix.tzinfo }}
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - if: startsWith(matrix.ruby, 'jruby-9.0')
         uses: philr/setup-ruby@legacy-v1
         with:
@@ -61,7 +61,7 @@ jobs:
           echo "::set-output name=os::`lsb_release -si`"
           echo "::set-output name=os_version::`lsb_release -sr`"
       - name: Cache tzdb
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: tzdb
           key: tzdb-${{ steps.determine_os_version.outputs.os }}-${{ steps.determine_os_version.outputs.os_version }}-${{ steps.determine_tzdata_version.outputs.tzdata_version }}