Update rake requirement from ~> 10.0 to ~> 13.0

Updates the requirements on [rake](https://github.com/ruby/rake) to permit the latest version.
- [Release notes](https://github.com/ruby/rake/releases)
- [Changelog](https://github.com/ruby/rake/blob/master/History.rdoc)
- [Commits](ruby/rake@v10.5.0...v13.0.1)

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -125,7 +125,7 @@ GEM
       method_source
       rake (>= 0.8.7)
       thor (>= 0.20.3, < 2.0)
-    rake (10.5.0)
+    rake (13.0.1)
     resonad (1.2.0)
     rspec (3.8.0)
       rspec-core (~> 3.8.0)
@@ -173,7 +173,7 @@ DEPENDENCIES
   bundler (~> 2.0)
   coveralls
   formify!
-  rake (~> 10.0)
+  rake (~> 13.0)
   rspec (~> 3.0)
 
 BUNDLED WITH

formify.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency 'bundler', '~> 2.0'
   spec.add_development_dependency 'coveralls', '>= 0'
-  spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'rake', '~> 13.0'
   spec.add_development_dependency 'rspec', '~> 3.0'
   spec.add_runtime_dependency 'rails'
   spec.add_runtime_dependency 'resonad'