Reenable full test matrix in GHA

Author: sungshik

.github/workflows/build.yaml

@@ -13,12 +13,12 @@ jobs:
     strategy:
       matrix:
         os:
-          #- image: ubuntu-latest
-          #- image: macos-latest
-            #mac-backend: jdk
+          - image: ubuntu-latest
+          - image: macos-latest
+            mac-backend: jdk
           - image: macos-latest
             mac-backend: fsevents
-          #- image: windows-latest
+          - image: windows-latest
         jdk: [11, 17, 21]
 
       fail-fast: false