Updated to Ruby 2.7.1
Updated to Ruby 2.7.1

Addresses the following security issues:

- CVE-2020-16255: Unsafe Object Creation Vulnerability in JSON
  (Additional fix)
- CVE-2020-10933: Heap exposure vulnerability in the socket library

[Details](https://chl.li/ljREu).

bkuhlmann/ruby_setup,bkuhlmann/ruby_setup