tailcfg: remove UserProfile.Groups

Removing as per go/group-all-the-things.

Updates tailscale/corp#17445

Signed-off-by: Maisem Ali <maisem@tailscale.com>

ipn/ipnlocal/local.go

@@ -3224,7 +3224,7 @@ func (b *LocalBackend) setPrefsLockedOnEntry(caller string, newp *ipn.Prefs) ipn
 			if !oldp.Persist().Valid() {
 				b.logf("active login: %s", newLoginName)
 			} else {
-				oldLoginName := oldp.Persist().UserProfile().LoginName()
+				oldLoginName := oldp.Persist().UserProfile().LoginName
 				if oldLoginName != newLoginName {
 					b.logf("active login: %q (changed from %q)", newLoginName, oldLoginName)
 				}