Remove unused .gitignore lines

These ignore built files that don't exist anymore, and just serve
to clutter up the .gitignore file. (I was initially confused when
I saw those lines, since I (correctly) thought that the only
Tailscale binaries were tailscale and tailscaled):

- taillogin was removed in d052586
- relaynode was removed in a56e853

Signed-off-by: Smitty <me@smitop.com>

.gitignore

@@ -6,8 +6,6 @@
 *.so
 *.dylib
 
-cmd/relaynode/relaynode
-cmd/taillogin/taillogin
 cmd/tailscale/tailscale
 cmd/tailscaled/tailscaled