Unskip RBS test on Windows for NoMemoryError workaround

test-unit 3.7.7 has been fixed this problem.

See also:
https://github.com/test-unit/test-unit/releases/tag/3.7.7

Author: tikkss

tool/rbs_skip_tests_windows

@@ -106,8 +106,6 @@ test_new(TempfileSingletonTest)
 # Errno::EACCES: Permission denied @ apply2files - C:/a/_temp/d20250813-10156-f8z9pn/test.gz
 test_open(ZlibGzipReaderSingletonTest)
 
-test_reachable_objects_from_root(ObjectSpaceTest) To avoid NoMemoryError with test-unit 3.7.5
-
 # Errno::EACCES: Permission denied @ rb_file_s_rename
 # D:/a/ruby/ruby/src/lib/rubygems/util/atomic_file_writer.rb:42:in 'File.rename'
 test_write_binary(GemSingletonTest)