Remove vendor directory and add it to the ignore list

vendor/golang.org/x/sys/.gitattributes

@@ -1,10 +0,0 @@
-# Treat all files in this repo as binary, with no git magic updating
-# line endings. Windows users contributing to Go will need to use a
-# modern version of git and editors capable of LF line endings.
-#
-# We'll prevent accidental CRLF line endings from entering the repo
-# via the git-review gofmt checks.
-#
-# See golang.org/issue/9281
-
-* -text