[hotfix] Update Flink versions in GitHub PR CI

Author: ferenc-csaky

.github/workflows/push_pr.yml

@@ -28,7 +28,7 @@ jobs:
   compile_and_test:
     strategy:
       matrix:
-        flink: [ 1.19.2, 1.20.1 ]
+        flink: [ 1.19.3, 1.20.3 ]
         jdk: [ '8, 11, 17, 21' ]
     uses: apache/flink-connector-shared-utils/.github/workflows/ci.yml@ci_utils
     with: