Remove package with security issue.

Did not run go mod tidy since I am archiving this today.

Author: mikeschinkel

go.sum

@@ -315,9 +315,6 @@ github.com/tomnomnom/linkheader v0.0.0-20180905144013-02ca5825eb80/go.mod h1:iFy
 github.com/tsuyoshiwada/go-gitcmd v0.0.0-20180205145712-5f1f5f9475df h1:Y2l28Jr3vOEeYtxfVbMtVfOdAwuUqWaP9fvNKiBVeXY=
 github.com/tsuyoshiwada/go-gitcmd v0.0.0-20180205145712-5f1f5f9475df/go.mod h1:pnyouUty/nBr/zm3GYwTIt+qFTLWbdjeLjZmJdzJOu8=
 github.com/ugorji/go v1.1.4/go.mod h1:uQMGLiO92mf5W77hV/PUCpI3pbzQx3CRekS0kk+RGrc=
-github.com/ulikunitz/xz v0.5.5/go.mod h1:2bypXElzHzzJZwzH67Y6wb67pO62Rzfn7BSiF4ABRW8=
-github.com/ulikunitz/xz v0.5.7 h1:YvTNdFzX6+W5m9msiYg/zpkSURPPtOlzbqYjrFn7Yt4=
-github.com/ulikunitz/xz v0.5.7/go.mod h1:nbz6k7qbPmH4IRqmfOplQw/tblSgqTqBwxkY0oWt/14=
 github.com/xanzy/ssh-agent v0.2.1 h1:TCbipTQL2JiiCprBWx9frJ2eJlCYT00NmctrHxVAr70=
 github.com/xanzy/ssh-agent v0.2.1/go.mod h1:mLlQY/MoOhWBj+gOGMQkOeiEvkx+8pJSI+0Bx9h2kr4=
 github.com/xiang90/probing v0.0.0-20190116061207-43a291ad63a2/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=