Can remove the strong dependency of swagger in 3.2 branch

[songxiaosheng]

• [ ] I have searched the issues of this repository and believe that this is not a duplicate.

Ask your question here

when i use spring boot project start application will throw such exception /dubbo-3.2.0-beta.3-SNAPSHOT.jar!/org/apache/dubbo/rpc/protocol/rest/integration/swagger/DubboSwaggerApiListingResource.class]: problem with class file or dependent class; nested exception is java.lang.NoClassDefFoundError: io/swagger/jaxrs/listing/BaseApiListingResource

[Phixsura]

Regarding the dependence of swagger, this was introduced in 2018, and it seems that this problem will only be caused when the protocol uses the rest protocol. I think this can be removed

[AlbumenJ]

Swagger should be a weak dependency for Dubbo