Increase credential_helper_test timeout (#28986)

### Description

### Motivation
This test flakily times out in CI pretty frequently.

### Build API Changes

No

### Checklist

- [ ] I have added tests for the new use cases (if any).
- [ ] I have updated the documentation (if applicable).

### Release Notes

RELNOTES: None

Closes #28986.

PiperOrigin-RevId: 883208467
Change-Id: Ideff68352a5bcba376f4dbad8401179bd32bc3e3

Author: fmeum

src/test/java/com/google/devtools/build/lib/authandtls/credentialhelper/BUILD

@@ -16,6 +16,7 @@ filegroup(
 
 java_test(
     name = "credentialhelper",
+    timeout = "long",
     srcs = glob(["*.java"]),
     data = [
         ":test_credential_helper",