[LOCAL] Update CI Matrix setup to match main

Author: cortinico

.github/workflows/pre-merge.yaml

@@ -21,11 +21,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ ubuntu-latest, macos-latest, windows-latest ]
-        jdk: [ 8, 11, 17 ]
-        exclude: # windows with JDK8 are *really* flaky
+        os: [ ubuntu-latest ]
+        jdk: [ 8, 11, 17, 21 ]
+        include:
           - os: windows-latest
-            jdk: 8
+            jdk: 21
+          - os: macos-latest
+            jdk: 21
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout Repo