Kill the rule suggesting the use of specific reduce block argument names

[vitormd]

I was about to complain about the rule suggesting the use of |a, e| as block params name for reduce and so I went to the style-guide used by rubocop and the last commit is this one:
commit.

Bottom line:

• A user should be allowed to choose other names for reduce block params. Such as

total_jobs = jobs.reduce { |sum, job| sum + job.count }

I am happy to come here create this issue so it gets updated immediately.

[bbatsov]

The cop should not be killed (some people likely find it useful), but I guess we can disable it by default.