bumpb rubocop version to 0.75

[raorao]

issue: #139 .

This PR moves us to depend on rubocop 0.75, in order to catch bug fixes. The one I'm specifically interested in is rubocop/rubocop#7170, but i thought it might be helpful to get us all the way up to date.

Changes required:

• nothing required to move from 0.72 -> 0.73 (test suite passed with no issue)
• nothing required to move from 0.73 -> 0.74 (test suite passed with no issue)
• following changes required to move from 0.74 -> 0.75:
  • remove use of SafeMode parameters for Performance/Count and Performance/Detect, as these were marked as removed. they were removed in rubocop-performance v1.5.0 (see Performance Count Cop does not work rubocop/rubocop-performance#69 (comment) for details), and marked as removed in Change warning location of SafeMode rubocop/rubocop#7341
  • test output change in test/standard/runners/rubocop_test.rb. To my untrained eye, the changes do not seem semantically meaningful.

If we are concerned about the changes necessary to get the move to 0.75 to work, happy to revert those and only bump to 0.74.

Thanks!

[majormoses]

LGTM

[searls]

Landed in 0.1.5

Note that writing "Fixes #139" or "Resolves #139" in the comment of a PR will automatically close a tagged issue upon merge of the PR.