While changing our build tools we were stumbling on outdated Man pages.

Although HTML4 support was already removed from Javadoc, the Man pages still show:
- default is HTML4 (incorrect) - this is not even true in LTS release 11
- shows options -html4 (no longer existing) and -html5 (now new default, but obsolete to show at all)
- allows to enable frames, which does not work

Interesting source parts: https://hg.openjdk.java.net/jdk/jdk/file/51fb05ec531d/src/jdk.javadoc/share/man/javadoc.1

Specifically:
- https://hg.openjdk.java.net/jdk/jdk/file/51fb05ec531d/src/jdk.javadoc/share/man/javadoc.1#l688
- https://hg.openjdk.java.net/jdk/jdk/file/51fb05ec531d/src/jdk.javadoc/share/man/javadoc.1#l636