ci: drop Node v12 from matrix

Why though?
Because Node v12 will soon be EOL'd once 16 becomes the stable LTS
next month and testing only 2 versions in our matrix will help ease
the pain (at least temporarily) caused by the docker hub rate limits.

Also upgraded the versions for 14 and 16 to the latest as of 2021-09-22

Also set the max parallel to 2 in order to closer match reallity
instead of 1024 which if we actually used the dockerhub rate limits
would fail all the tests anyway.

Signed-off-by: Peter Somogyvari <peter.somogyvari@accenture.com>

.github/workflows/ci.yml

@@ -11,15 +11,14 @@ on:
 jobs:
   build:
     runs-on: ${{ matrix.os }}
-    continue-on-error: ${{ matrix.experimental }}
+    continue-on-error: false
 
     strategy:
       fail-fast: false
-      max-parallel: 1024
+      max-parallel: 2
       matrix:
         os: [ubuntu-20.04]
-        node-version: [v12.22.3, v14.15.1, v16.2.0]
-        experimental: [false]
+        node-version: [v14.17.6, v16.9.1]
 
     steps:
     - name: Set Swap Space to 10GB