Update rake requirement from ~> 12.3.3 to ~> 13.2.1

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@v12.3.3...v13.2.1)

---
updated-dependencies:
- dependency-name: rake
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    opsgenie-schedule (0.1.4)
+    opsgenie-schedule (0.1.6)
       httparty (~> 0.17)
 
 GEM
@@ -34,7 +34,7 @@ GEM
     public_suffix (6.0.1)
     racc (1.8.1)
     rainbow (3.1.1)
-    rake (12.3.3)
+    rake (13.2.1)
     regexp_parser (2.9.2)
     rexml (3.3.8)
     rspec (3.13.0)
@@ -82,7 +82,7 @@ DEPENDENCIES
   dotenv (~> 2.7)
   opsgenie-schedule!
   pry (~> 0.14.0)
-  rake (~> 12.3.3)
+  rake (~> 13.2.1)
   rspec (~> 3.0)
   standard (~> 0.1)
   webmock (~> 3.5)

opsgenie-schedule.gemspec

@@ -22,7 +22,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "bundler", "~> 2.0"
   spec.add_development_dependency "pry", "~> 0.14.0"
-  spec.add_development_dependency "rake", "~> 12.3.3"
+  spec.add_development_dependency "rake", "~> 13.2.1"
   spec.add_development_dependency "rspec", "~> 3.0"
   spec.add_development_dependency "standard", "~> 0.1"
   spec.add_development_dependency "webmock", "~> 3.5"