Fix workflow.

Author: davidlehn

.github/workflows/main.yml

@@ -24,8 +24,7 @@ jobs:
     strategy:
       matrix:
         node-version: [14.x]
-        env:
-          BUNDLER: [webpack, browserify]
+        bundler: [webpack, browserify]
     steps:
     - uses: actions/checkout@v2
     - name: Use Node.js ${{ matrix.node-version }}
@@ -35,6 +34,8 @@ jobs:
     - run: npm install
     - name: Run karma tests
       run: npm run test-karma
+      env:
+        BUNDLER: ${{ matrix.bundler }}
   lint:
     runs-on: ubuntu-latest
     timeout-minutes: 10