[Fix #7042] Remove post install message for RuboCop Performance
[Fix #7042] Remove post install message for RuboCop Performance

Closes #7042.

Since a migration period to extract RuboCop Performance is over,
this PR removes post install message.

rrosenblum/rubocop,meganemura/rubocop,tdeo/rubocop,jfelchner/rubocop,mikegee/rubocop,tejasbubane/rubocop,rrosenblum/rubocop,smakagon/rubocop,vergenzt/rubocop,jmks/rubocop,deivid-rodriguez/rubocop,panthomakos/rubocop,vergenzt/rubocop,maxjacobson/rubocop,panthomakos/rubocop,meganemura/rubocop,jmks/rubocop,jmks/rubocop,tdeo/rubocop,tejasbubane/rubocop,jfelchner/rubocop,maxjacobson/rubocop,panthomakos/rubocop,deivid-rodriguez/rubocop,vergenzt/rubocop,rrosenblum/rubocop,smakagon/rubocop,jfelchner/rubocop,mikegee/rubocop,bbatsov/rubocop,tejasbubane/rubocop,tdeo/rubocop,deivid-rodriguez/rubocop,maxjacobson/rubocop,mikegee/rubocop,bbatsov/rubocop,meganemura/rubocop