Clean up our actions/cache step

Removed name because it was not more informative than the default. Swapped out
a hardcoded job reference for the github.job context value. Switch the base
cache key to a step environment value so we can set it once and reuse. Removed
additional restore-key value that might have undesirable results.

.github/workflows/build.yml

@@ -20,22 +20,20 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: 3.9
-      - name: Cache linting environments
-        uses: actions/cache@v2
+      - uses: actions/cache@v2
+        env:
+          BASE_CACHE_KEY: "${{ github.job }}-${{ runner.os }}-\
+            py${{ steps.setup-python.outputs.python-version }}-"
         with:
           path: |
             ${{ env.PIP_CACHE_DIR }}
             ${{ env.PRE_COMMIT_CACHE_DIR }}
-          key: |
-            lint-${{ runner.os }}-\
-            py${{ steps.setup-python.outputs.python-version }}-\
+          key: "${{ env.BASE_CACHE_KEY }}\
             ${{ hashFiles('**/requirements-test.txt') }}-\
             ${{ hashFiles('**/requirements.txt') }}-\
             ${{ hashFiles('**/.pre-commit-config.yaml') }}"
           restore-keys: |
-            lint-${{ runner.os }}-\
-            py${{ steps.setup-python.outputs.python-version }}-
-            lint-${{ runner.os }}-
+            ${{ env.BASE_CACHE_KEY }}
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip