ojluni: delete dead native (.c) code.

These files were added in commit 51b1b699
("Initial import of OpenJdk files.") but are no longer used (I didn't
check whether they were ever used in the past). Specifically, they are
not listed in ojluni/src/main/native/Android.bp so they're not compiled.

This CL removes these unused .c files.

Test: make droid cts
Test: Treehugger
Bug: 77572714

Change-Id: Id1a52b0a0d8db323641459e23d2f1f4c34688e68