#1411 Deprecate UseConcurrentHashMap rule

[Michał Kordas]

This rule is very confusing one. Replacing all occurrences of HashMap with ConcurrentHashMap by some newbie may cause huge problems: https://ria101.wordpress.com/2011/12/12/concurrenthashmap-avoid-a-common-misuse/

ConcurrentHashMap is special collection and people knowing how to use it properly will know also where to use it. No additional rule is needed for that.

[Andreas Dangel]

See also [#1336]