ci: fix typo in lint matrix setup

`env.node-version` was undefined (`matrix.node-version` was defined, but never used), therefore the linting used to run in Node.js 14

Author: dominykas

.github/workflows/nodejs.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        node-version: [12.x]
+        node-version: [14.x]
 
     runs-on: ${{ matrix.os }}
 
@@ -29,10 +29,10 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Use Node.js ${{ env.node-version }}
+      - name: Use Node.js ${{ matrix.node-version }}
         uses: actions/setup-node@v1
         with:
-          node-version: ${{ env.node-version }}
+          node-version: ${{ matrix.node-version }}
 
       - name: Use latest NPM
         run: sudo npm i -g npm