revert grape version

Author: thogg4

grape-swagger.gemspec

@@ -14,7 +14,7 @@ Gem::Specification.new do |s|
   s.license     = 'MIT'
 
   s.required_ruby_version = '>= 2.2.6'
-  s.add_runtime_dependency 'grape', '>= 0.19.1'
+  s.add_runtime_dependency 'grape', '>= 0.16.2'
 
   s.files         = `git ls-files`.split("\n")
   s.test_files    = `git ls-files -- {test,spec}/*`.split("\n")