Use modelNameMappings in ruby client

The modelNameMappings were introduced with PRs OpenAPITools#16209, OpenAPITools#16234 and are
now also used in the ruby client generator.

Author: tschoppi

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyClientCodegen.java

@@ -410,6 +410,10 @@ public String toModelName(final String name) {
             return schemaMapping.get(name);
         }
 
+        if (modelNameMapping.containsKey(name)) {
+            return modelNameMapping.get(name);
+        }
+
         // memoization
         String origName = name;
         if (schemaKeyToModelNameCache.containsKey(origName)) {