Fix extending protected nested java classes #33008

Job	Run time
test_non_bootstrapped	0s
test	55m 23s
test_scala2_library_tasty	0s
test_windows_fast	52m 51s
community_build_a	52m 47s
MiMa	11m 18s
test_windows_full	0s
community_build_b	1h 33m 19s
community_build_c	1h 1m 26s
test_sbt	18m 15s
test_java8	0s
build-msi-package	0s
build-sdk-package / build	7m 54s
test-msi-package	0s
build-chocolatey-package / build	22s
test-chocolatey-package	0s
publish_nightly	0s
publish_release	0s
nightly_documentation	0s
open_issue_on_failure	0s
	5h 53m 35s

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