RFR: 8274425: Remove unused Modules.extraLimitMods [v2]

[Andrey Turbanov]

> HashSet `com.sun.tools.javac.comp.Modules.extraLimitMods` is always empty. Code only check its content, but no content added.
> There was a method `addExtraLimitModules`, but it was removed under [JDK-8175191](https://bugs.openjdk.java.net/browse/JDK-8175191) 253fdcd0b26
> Method `addExtraLimitModules` itself was added in ec9ca2997f4, but was never actually used .

Andrey Turbanov has updated the pull request incrementally with one additional commit since the last revision:

  8274425: Remove unused Modules.extraLimitMods
  
  update copyright year

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5628/files
  - new: https://git.openjdk.java.net/jdk/pull/5628/files/72bf4ca3..54113676

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5628&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5628&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5628.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5628/head:pull/5628

PR: https://git.openjdk.java.net/jdk/pull/5628