chore: downgrade to node 16 to fix the build job

With Node 17 we are having the following message: `Error:
error:0308010C:digital envelope routines::unsupported`. Downgrading to Node 16
seems better than forcing `export NODE_OPTIONS=--openssl-legacy-provider` and
possibly running with [known insecure
SSL](https://www.openssl.org/docs/manmaster/man7/OSSL_PROVIDER-legacy.html).

Reference:
webpack/webpack#14532 (comment)

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [14.x, 17.x]
+        node-version: [14.x, 16.x]
 
     steps:
       - uses: actions/checkout@v2