G1 GC testcases not applicable to jdk8 arm32 linux

[smlambert]

See #4984 (comment) and seen in https://ci.adoptium.net/job/Grinder/8657/ - G1 GC is disabled in this release for jdk8 arm32 linux

TEST: gc/ergonomics/TestDynamicNumberOfGCThreads.java
TEST: gc/class_unloading/TestG1ClassUnloadingHWM.java
Test results: passed: 718; failed: 2

These 2 hotspot_jre testcases are testing G1 GC, which is disabled on arm_linux JDK8, so these testcases should be excluded for this platform/version.

07:56:20   stderr: [OpenJDK Client VM warning: G1 GC is disabled in this release.
07:56:20  ]
07:56:20   exitValue = 0
07:56:20  
07:56:20  java.lang.RuntimeException: 'new_active_workers' missing from stdout/stderr 
07:56:20  
07:56:20  	at com.oracle.java.testlibrary.OutputAnalyzer.shouldContain(OutputAnalyzer.java:134)
07:56:20  	at TestDynamicNumberOfGCThreads.verifyDynamicNumberOfGCThreads(TestDynamicNumberOfGCThreads.java:48)
07:56:20  	at TestDynamicNumberOfGCThreads.testDynamicNumberOfGCThreads(TestDynamicNumberOfGCThreads.java:57)
07:56:20  	at TestDynamicNumberOfGCThreads.main(TestDynamicNumberOfGCThreads.java:41)
07:56:20  	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
07:56:20  	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
07:56:20  	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
07:56:20  	at java.lang.reflect.Method.invoke(Method.java:498)
07:56:20  	at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:298)
07:56:20  	at java.lang.Thread.run(Thread.java:750)
07:56:20  
07:56:20  JavaTest Message: Test threw exception: java.lang.RuntimeException
07:56:20  JavaTest Message: shutting down test
07:56:20  
07:56:20  
07:56:20  TEST RESULT: Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: 'new_active_workers' missing from stdout/stderr

The exclusion should happen upstream in the https://github.com/adoptium/aarch32-jdk8u.git repository, but in the meantime can be held in the problem list of this repository.