Use seperate node_modules for Firestore tests

Author: dlarocque

.github/workflows/test-changed-firestore.yml

@@ -131,7 +131,7 @@ jobs:
         id: node_modules
         with:
           path: "**/node_modules"
-          key: node_modules-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          key: node_modules-firestore-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
       - run: yarn install --frozen-lockfile
       - name: install Chrome stable
         run: |