Remove unused .rubocop.yml.
ruby22.y: ensure correct scope of arguments.

This commit tracks upstream commit ruby/ruby@01740f0c2.

Note that this commit includes no functional changes. Parser already
implements correct semantics since ruby21.y.
- ruby22.y: "tap (proc do end)": allow parenthesed do-block in cmdarg.

This commit tracks upstream commit ruby/ruby@c5013452.