Update httparty requirement from ~> 0.18.0 to >= 0.18, < 0.22

Updates the requirements on [httparty](https://github.com/jnunemaker/httparty) to permit the latest version.
- [Release notes](https://github.com/jnunemaker/httparty/releases)
- [Changelog](https://github.com/jnunemaker/httparty/blob/master/Changelog.md)
- [Commits](jnunemaker/httparty@v0.18.0...v0.21.0)

---
updated-dependencies:
- dependency-name: httparty
  dependency-type: direct:production
...

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

Gemfile.lock

@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     applocale-ruby (0.0.10)
-      httparty (~> 0.18.0)
+      httparty (>= 0.18, < 0.22)
       thor (>= 0.18.0)
 
 GEM
@@ -12,13 +12,11 @@ GEM
     ast (2.4.0)
     builder (3.2.4)
     coderay (1.1.2)
-    httparty (0.18.0)
-      mime-types (~> 3.0)
+    httparty (0.21.0)
+      mini_mime (>= 1.0.0)
       multi_xml (>= 0.5.2)
     method_source (1.0.0)
-    mime-types (3.3.1)
-      mime-types-data (~> 3.2015)
-    mime-types-data (3.2020.0512)
+    mini_mime (1.1.2)
     minitest (5.14.0)
     minitest-reporters (1.4.2)
       ansi

applocale-ruby.gemspec

@@ -29,7 +29,7 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = ">= 2.3.0"
 
-  spec.add_dependency "httparty", "~> 0.18.0"
+  spec.add_dependency "httparty", ">= 0.18", "< 0.22"
   spec.add_dependency "thor", ">= 0.18.0"
 
   spec.add_development_dependency "bundler", "~> 2.0"