internal/dl: remove unlikely releasers from validUser

This change removes adg, bradfitz, cbro, andybons and julieqiu from
the list of valid users. They are not expected to be releasing Go at
any point in the near future.

Change-Id: I38fd878f4c9487402ad61bab8b3d8c6437dd9763
Reviewed-on: https://go-review.googlesource.com/c/website/+/305689
Trust: Carlos Amedee <carlos@golang.org>
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

internal/dl/dl.go

@@ -330,9 +330,11 @@ func parseVersion(v string) (maj, min int, tail string) {
 	return
 }
 
+// validUser controls whether the named gomote user is allowed to upload
+// Go release binaries via the /dl/upload endpoint.
 func validUser(user string) bool {
 	switch user {
-	case "adg", "bradfitz", "cbro", "andybons", "valsorda", "dmitshur", "katiehockman", "julieqiu", "rakoczy", "amedee", "cherryyz", "drchase", "mknyszek":
+	case "amedee", "cherryyz", "dmitshur", "drchase", "katiehockman", "mknyszek", "rakoczy", "valsorda":
 		return true
 	}
 	return false