[BUG][aspnetcore] Documentation : operationModifier can't be partial

Created by: tmakin

Description

Very minor issue.

The help text for aspnetcore generator suggests that the operationModifier option can be partial. This is not possible in c# and is not implemented in the generator (it's just the help text that is wrong) https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AspNetCoreServerCodegen.java#L73

openapi-generator version

4.2.2

Steps to reproduce

Using CLI:

> openapi-generator config-help -g aspnetcore

...
 operationModifier
            Operation Modifier can be virtual, abstract or partial (Default: virtual)
...

Suggest a fix

Update help text as follows: private CliOption operationModifier = new CliOption(OPERATION_MODIFIER, "Operation Modifier can be virtual or abstract");