Fix syncbot permissions for fork PRs by using `pull_request_target` #800

Job	Run time
ci-gate	4s
Script unit tests	5s
[jvm-build-test-java21]: quarkus3	5m 9s
[jvm-build-test-java25]: springboot3-leyden	4m 26s
[jvm-build-test-java25]: springboot4	3m 51s
[jvm-build-test-java21]: quarkus3-spring-compatibility	5m 22s
[jvm-build-test-java21]: springboot4	3m 57s
[jvm-build-test-java25]: springboot3	4m 15s
[jvm-build-test-java25]: springboot3-virtual	3m 57s
[jvm-build-test-java21]: springboot4-virtual	3m 51s
[jvm-build-test-java25]: springboot3-virtual-leyden	4m 27s
[jvm-build-test-java21]: quarkus3-virtual	5m 40s
[jvm-build-test-java21]: springboot3-virtual	4m 6s
[jvm-build-test-java21]: springboot3	4m 8s
[jvm-build-test-java25]: quarkus3-leyden	5m 10s
[jvm-build-test-java25]: springboot4-virtual	3m 56s
[jvm-build-test-java25]: quarkus3-virtual	5m 3s
[jvm-build-test-java25]: quarkus3	10s
[jvm-build-test-java25]: quarkus3-spring-compatibility	5m 31s
[jvm-build-test-java25]: quarkus3-virtual-leyden	5m 13s
[jvm-build-test-java25]: springboot4-leyden	4m 20s
[jvm-build-test-java25]: springboot4-virtual-leyden	4m 36s
	1h 27m 17s

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