Cache node_modules

Don't cache the yarn cache, since we need to build fresh packages even
when we copy files from the yarn cache into node_modules.

.github/workflows/doc-tests.yaml

@@ -47,17 +47,10 @@ jobs:
           repository: "gravitational/docs"
           path: "docs"
 
-        # Set up caching for node_modules across workflow runs.
-        # The following two steps are based on this example:
-        # https://github.com/actions/cache/blob/6849a6489940f00c2f30c0fb92c6274307ccb58a/examples.md#node---yarn
-      - name: Get yarn cache directory path
-        id: yarn-cache-dir-path
-        run: echo "dir=$(yarn cache dir)" >> $GITHUB_OUTPUT
-
       - uses: actions/cache@v4
         id: yarn-cache # use this to check for `cache-hit` (`steps.yarn-cache.outputs.cache-hit != 'true'`)
         with:
-          path: ${{ steps.yarn-cache-dir-path.outputs.dir }}
+          path: '${{ github.workspace }}/docs/node_modules'
           key: ${{ runner.os }}-yarn-${{ hashFiles(format('{0}/docs/yarn.lock', github.workspace)) }}
           restore-keys: |
             ${{ runner.os }}-yarn-