Fix JSON print in Ruby (#1274)

It turns out that `to_h` is not a method available on every object
returned by the samples at the moment. Also, there's some kind of
decoding bug showing up in certain samples where the JSON module is
unable to unparse the response.

It's troublesome to have so much boilerplate just to pretty print. This
commit removes the pretty calls in favor of the vanilla `to_json` method
implemented by the base model class in the Ruby client. In the future,
once the bugs w.r.t `pretty_generate` have been resolved, we can revert.

src/main/resources/com/google/api/codegen/ruby/sample.snip

@@ -23,9 +23,6 @@
     require 'googleauth'
   @end
   require '{@class.serviceRequirePath}'
-  @if class.hasResponse
-    require 'json'
-  @end
 
   {@class.serviceVarName} = {@class.serviceTypeNamespace}::{@class.serviceTypeName}.new
 
@@ -116,22 +113,22 @@
     @if class.pageStreaming.isResourceMap
       {@class.pageStreaming.pageVarName}.each do |{@class.pageStreaming.resourceKeyVarName}, {@class.pageStreaming.resourceValueVarName}|
         @# TODO: Change code below to process each ({@class.pageStreaming.resourceKeyVarName}, {@class.pageStreaming.resourceValueVarName}) pair:
-        puts String({@class.pageStreaming.resourceKeyVarName} << " => " << JSON.pretty_unparse({@class.pageStreaming.resourceValueVarName}.to_h)
+        puts String({@class.pageStreaming.resourceKeyVarName} << " => " << {@class.pageStreaming.resourceValueVarName}.to_json
       end
     @else
       # We don't handle non-repeated page streaming resources separately in Ruby
       # because the fetch_all treats them correctly.
       {@class.pageStreaming.pageVarName}.each do |{@class.pageStreaming.resourceVarName}|
         @# TODO: Change code below to process each `{@class.pageStreaming.resourceVarName}` resource:
-        puts JSON.pretty_unparse({@class.pageStreaming.resourceVarName}.to_h)
+        puts {@class.pageStreaming.resourceVarName}.to_json
       end
     @end
   @else
     @if class.hasResponse
       {@class.responseVarName} = {@methodCall(class)}({@paramList(class.methodCallFieldVarNames)})
 
       @# TODO: Change code below to process the `{@class.responseVarName}` object:
-      puts JSON.pretty_unparse({@class.responseVarName}.to_h)
+      puts {@class.responseVarName}.to_json
     @else
       {@methodCall(class)}({@paramList(class.methodCallFieldVarNames)})
     @end