fix warning in swagger json/yaml generator (#4827)

Author: wing328

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/SwaggerGenerator.java

@@ -52,4 +52,16 @@ public void processSwagger(Swagger swagger) {
             LOGGER.error(e.getMessage(), e);
         }
     }
+
+    @Override
+    public String escapeQuotationMark(String input) { 
+        // just return the original string
+        return input;
+    } 
+
+    @Override
+    public String escapeUnsafeCharacters(String input) { 
+        // just return the original string
+        return input;
+    }  
 }

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/SwaggerYamlGenerator.java

@@ -61,4 +61,17 @@ public void processSwagger(Swagger swagger) {
             LOGGER.error(e.getMessage(), e);
         }
     }
+
+    @Override
+    public String escapeQuotationMark(String input) {
+        // just return the original string
+        return input;
+    }
+
+    @Override
+    public String escapeUnsafeCharacters(String input) {
+        // just return the original string
+        return input;
+    }   
+
 }