Log Message:
devel/ruby-concurrent-ruby: update to 1.1.7

Update ruby-concurrent-ruby to 1.1.7.

## Release v1.1.7 (6 August 2020)

concurrent-ruby:

* (#879) Consider falsy value on
  `Concurrent::Map#compute_if_absent` for fast non-blocking path
* (#876) Reset Async queue on forking, makes Async fork-safe
* (#856) Avoid running problematic code in RubyThreadLocalVar on
  MRI that occasionally results in segfault
* (#853) Introduce ThreadPoolExecutor without a Queue