use cpp oatapp test spec (#21601)

Author: wing328

bin/configs/cpp-oatpp-server-cpp-oatpp.yaml

@@ -1,6 +1,6 @@
 generatorName: cpp-oatpp-server
 outputDir: samples/server/petstore/cpp-oatpp
-inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore.yaml
+inputSpec: modules/openapi-generator/src/test/resources/3_0/cpp-oatpp-server/petstore.yaml
 templateDir: modules/openapi-generator/src/main/resources/cpp-oatpp-server
 additionalProperties:
   addExternalLibs: "true"