oauth1 test_realm_validation: fix expected signature
oauth1 test_realm_validation: fix expected signature

This error was previously masked due to return value (False, <request>)
being always treated as True.

garciasolero/oauthlib,oauthlib/oauthlib,armersong/oauthlib,singingwolfboy/oauthlib,masci/oauthlib,mick88/oauthlib,lepture/oauthlib,lepture/oauthlib,metatoaster/oauthlib,idan/oauthlib,Blitzen/oauthlib,masci/oauthlib,skion/oauthlib-oidc,flamusdiu/oauthlib,barseghyanartur/oauthlib,hirokiky/oauthlib,bjmc/oauthlib,cyrilchaponeverysens/oauthlib,flamusdiu/oauthlib