Correct OpenAPITools#9916, fix Produces instances

While the fix in OpenAPITools#9916 correctly made endpoint types which did not
produce content return the `NoContent` type, those endpoint still
generated `Produces` instances with the wrong mime types due to not
resetting the `hasProduces` variable. This corrects that fix so that the
`Produces` instance for `MimeNoContent` is generated instead of any
other instance.

Author: ivanbakel

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

@@ -881,6 +881,7 @@ private void processReturnType(CodegenOperation op) {
         if (returnType == null || returnType.equals("null")) {
             returnType = "NoContent";
             SetNoContent(op, VENDOR_EXTENSION_X_INLINE_ACCEPT);
+            op.hasProduces = false;
         }
         if (returnType.contains(" ")) {
             returnType = "(" + returnType + ")";