[Jtreg/FFI] Disable FFI related test suite in JDK20 (#4318)

The change is to exclude the FFI related test cases
in AttachTest.java captured at
eclipse-openj9/openj9#16656
given the FFI related code in JDK20 has been disabled
for the moment and will be enabled once the code has
been updated against the latest APIs.

Signed-off-by: ChengJin01 <jincheng@ca.ibm.com>

openjdk/excludes/ProblemList_openjdk20-openj9.txt

@@ -160,6 +160,8 @@ jdk/modules/etc/DefaultModules.java https://github.com/eclipse-openj9/openj9/iss
 jdk/modules/incubator/ImageModules.java https://github.com/adoptium/aqa-tests/issues/1267 macosx-all
 jni/nullCaller/NullCallerTest.java https://github.com/eclipse-openj9/openj9/issues/15370 linux-ppc64le,macosx-all
 
+java/lang/Thread/jni/AttachCurrentThread/AttachTest.java#id1 https://github.com/eclipse-openj9/openj9/issues/16656 generic-all
+
 ############################################################################
 
 # jdk_internal