Simplify to_json calls

src/spectator/errored_result.cr

@@ -43,7 +43,7 @@ module Spectator
       json.object do
         json.field("type", error.class.to_s)
         json.field("message", error.message)
-        json.field("backtrace") { error.backtrace.to_json(json) }
+        json.field("backtrace", error.backtrace)
       end
     end
   end

src/spectator/expectations/expectation.cr

@@ -44,9 +44,9 @@ module Spectator::Expectations
     # Creates the JSON representation of the expectation.
     def to_json(json : ::JSON::Builder)
       json.object do
-        json.field("satisfied") { satisfied?.to_json(json) }
-        json.field("expected") { expected_message.to_json(json) }
-        json.field("actual") { actual_message.to_json(json) }
+        json.field("satisfied", satisfied?)
+        json.field("expected", expected_message)
+        json.field("actual", actual_message)
         json.field("values") do
           json.object do
             values.each do |labeled_value|

src/spectator/finished_result.cr

@@ -21,7 +21,7 @@ module Spectator
     private def add_json_fields(json : ::JSON::Builder)
       super
       json.field("time", elapsed.to_s)
-      json.field("expectations") { expectations.to_json(json) }
+      json.field("expectations", expectations)
     end
   end
 end

src/spectator/result.cr

@@ -32,8 +32,8 @@ module Spectator
 
     # Adds the common fields for a result to a JSON builder.
     private def add_json_fields(json : ::JSON::Builder)
-      json.field("name") { example.to_json(json) }
-      json.field("location") { example.source.to_json(json) }
+      json.field("name", example)
+      json.field("location", example.source)
       json.field("result", to_s)
     end
   end