regression: restore dateSerializers in scala sttp 4 client gen (#23845)

* regression: restore dateSerializers in scala sttp 4 client gen

* update

Author: wing328

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4ClientCodegen.java

@@ -174,6 +174,7 @@ public void processOpts() {
         supportingFiles.add(new SupportingFile("jsonSupport.mustache", invokerFolder, "JsonSupport.scala"));
         supportingFiles.add(new SupportingFile("additionalTypeSerializers.mustache", invokerFolder, "AdditionalTypeSerializers.scala"));
         supportingFiles.add(new SupportingFile("project/build.properties.mustache", "project", "build.properties"));
+        supportingFiles.add(new SupportingFile("dateSerializers.mustache", invokerFolder, "DateSerializers.scala"));
         supportingFiles.add(new SupportingFile("project/plugins.mustache", "project", "plugins.sbt"));
         supportingFiles.add(new SupportingFile("scalafmt.mustache", "", ".scalafmt.conf"));
     }

samples/client/petstore/scala-sttp4/.openapi-generator/FILES

@@ -7,6 +7,7 @@ src/main/scala/org/openapitools/client/api/PetApi.scala
 src/main/scala/org/openapitools/client/api/StoreApi.scala
 src/main/scala/org/openapitools/client/api/UserApi.scala
 src/main/scala/org/openapitools/client/core/AdditionalTypeSerializers.scala
+src/main/scala/org/openapitools/client/core/DateSerializers.scala
 src/main/scala/org/openapitools/client/core/JsonSupport.scala
 src/main/scala/org/openapitools/client/model/ApiResponse.scala
 src/main/scala/org/openapitools/client/model/Category.scala