[actions] pin codecov to v3.1.5

this is the only one that supports node 20, and also tokenless upload

Author: ljharb

.github/workflows/node-4+.yml

@@ -102,7 +102,7 @@ jobs:
       - run: rm __tests__/src/util/getComputedRole-test.js
         if: ${{ matrix.node-version < 7 }}
       - run: npm run test:ci
-      - uses: codecov/codecov-action@v3
+      - uses: codecov/codecov-action@v3.1.5
 
   node:
     name: 'node 4+'