Get rid of utf8 chars in two tests

These two langtools jtreg test files contain a utf8 char:
test/tools/javac/api/6437999/Utf8.java:25: * @author Peter von der AhÃ©
test/tools/javac/api/T6306137.java:30: * @author Peter von der AhÃ©

They should contain only ASCII. The tests should generate the need files containing the utf8 chars so that the chars themselves are not in the source code in the repository.