Track 8.19 branch instead of 8.x for jdk compat tests (#17576)

The 8.x branch has been renamed 8.19. Reflect this in jdk test config.

Author: donoghuc

catalog-info.yaml

@@ -793,8 +793,8 @@ spec:
           message: Weekly trigger of JDK update availability pipeline per branch
           env:
             PIPELINES_TO_TRIGGER: 'logstash-jdk-availability-check-pipeline'
-        Weekly JDK availability check (8.x):
-          branch: 8.x
+        Weekly JDK availability check (8.19):
+          branch: 8.19
           cronline: 0 2 * * 1  # every Monday@2AM UTC
           message: Weekly trigger of JDK update availability pipeline per branch
           env: