Fix revoked certificate tests to use more stable external party server (#31245)
Fix revoked certificate tests to use more stable external party server (#31245)

System.Net.Http.Functional.Tests.SocketsHttpHandler_HttpClientHandler_ServerCertificates_Test.NoCallback_RevokedCertificate_NoRevocationChecking_Succeeds tests was failing because the external third-party server we use is no longer working.

Switching to the more reliable *.badssl.com servers will fix this.
mmitche/corefx,BrennanConroy/corefx,mmitche/corefx,ViktorHofer/corefx,Jiayili1/corefx,ptoonen/corefx,shimingsg/corefx,Jiayili1/corefx,wtgodbe/corefx,ViktorHofer/corefx,wtgodbe/corefx,ericstj/corefx,Jiayili1/corefx,wtgodbe/corefx,mmitche/corefx,ptoonen/corefx,ptoonen/corefx,ptoonen/corefx,ericstj/corefx,ViktorHofer/corefx,shimingsg/corefx,BrennanConroy/corefx,ViktorHofer/corefx,ViktorHofer/corefx,BrennanConroy/corefx,mmitche/corefx,ViktorHofer/corefx,shimingsg/corefx,ericstj/corefx,ericstj/corefx,Jiayili1/corefx,wtgodbe/corefx,ptoonen/corefx,wtgodbe/corefx,Jiayili1/corefx,ericstj/corefx,shimingsg/corefx,mmitche/corefx,ptoonen/corefx,shimingsg/corefx,Jiayili1/corefx,mmitche/corefx,ptoonen/corefx,Jiayili1/corefx,shimingsg/corefx,shimingsg/corefx,ericstj/corefx,ViktorHofer/corefx,wtgodbe/corefx,wtgodbe/corefx,ericstj/corefx,mmitche/corefx