Update rubocop requirement from ~> 1.15.0 to ~> 1.16.0

Updates the requirements on [rubocop](https://github.com/rubocop/rubocop) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop@v1.15.0...v1.16.0)

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -39,16 +39,16 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.10.0)
     rspec-support (3.10.0)
-    rubocop (1.15.0)
+    rubocop (1.16.0)
       parallel (~> 1.10)
       parser (>= 3.0.0.0)
       rainbow (>= 2.2.2, < 4.0)
       regexp_parser (>= 1.8, < 3.0)
       rexml
-      rubocop-ast (>= 1.5.0, < 2.0)
+      rubocop-ast (>= 1.7.0, < 2.0)
       ruby-progressbar (~> 1.7)
       unicode-display_width (>= 1.4.0, < 3.0)
-    rubocop-ast (1.5.0)
+    rubocop-ast (1.7.0)
       parser (>= 3.0.1.1)
     ruby-progressbar (1.11.0)
     simplecov (0.16.1)
@@ -71,7 +71,7 @@ DEPENDENCIES
   bundler (~> 2.2.16)
   coveralls (~> 0.8.23)
   rspec (~> 3.10.0)
-  rubocop (~> 1.15.0)
+  rubocop (~> 1.16.0)
   turkish_cities!
 
 BUNDLED WITH

turkish_cities.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'bundler', '~> 2.2.16'
   s.add_development_dependency 'coveralls', '~> 0.8.23'
   s.add_development_dependency 'rspec', '~> 3.10.0'
-  s.add_development_dependency 'rubocop', '~> 1.15.0'
+  s.add_development_dependency 'rubocop', '~> 1.16.0'
 
   if s.respond_to?(:metadata)
     s.metadata['changelog_uri'] = 'https://github.com/sarslanoglu/turkish_cities/blob/master/CHANGELOG.md'