gnu: ruby-rubocop: Update to 0.88.0.

gnu: ruby-rubocop: Update to 0.88.0.

* gnu/packages/patches/ruby-rubocop-break-dependency-cycle.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register patch.
* gnu/packages/ruby.scm (ruby-rubocop): Update to 0.88.0.
[origin]: Use git-fetch.  Apply the newly added patch.
[arguments]: Set #:test-target to "default".  Remove #:tests?, enabling tests.
[phases]{remove-problematic-tests, disable-bundler, set-home,
make-adoc-files-writable}: New phases.  Replace the 'replace-git-ls-files
phase.
[native-inputs]: Add ruby-bump, ruby-pry, ruby-rspec, ruby-test-queue,
ruby-webmock-2 and ruby-yard.
[propagated-inputs]: Remove ruby-powerpack and ruby-jaro-winkler.  Add
ruby-regexp-parser, ruby-rexml and ruby-rubocop-ast.