Fix syncbot permissions for fork PRs by using `pull_request_target` #803

Job	Run time
ci-gate	3s
Script unit tests	4s
[jvm-build-test-java21]: quarkus3	4m 50s
[jvm-build-test-java25]: springboot3	4m 4s
[jvm-build-test-java21]: springboot3	4m 38s
[jvm-build-test-java21]: quarkus3-spring-compatibility	5m 21s
[jvm-build-test-java21]: springboot4-virtual	4m 8s
[jvm-build-test-java25]: springboot3-leyden	4m 27s
[jvm-build-test-java21]: springboot3-virtual	4m 9s
[jvm-build-test-java21]: quarkus3-virtual	4m 39s
[jvm-build-test-java21]: springboot4	4m 6s
[jvm-build-test-java25]: quarkus3-leyden	5m 52s
[jvm-build-test-java25]: springboot4	3m 48s
[jvm-build-test-java25]: quarkus3-virtual	4m 59s
[jvm-build-test-java25]: springboot4-leyden	4m 54s
[jvm-build-test-java25]: quarkus3-spring-compatibility	5m 11s
[jvm-build-test-java25]: quarkus3	5m 15s
[jvm-build-test-java25]: quarkus3-virtual-leyden	4m 58s
[jvm-build-test-java25]: springboot4-virtual-leyden	4m 31s
[jvm-build-test-java25]: springboot4-virtual	3m 48s
[jvm-build-test-java25]: springboot3-virtual	3m 59s
[jvm-build-test-java25]: springboot3-virtual-leyden	4m 24s
	1h 32m 8s

Provide feedback