wgengine/magicsock: use netaddr.MustParseIPPrefix

Delete our bespoke helper.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

wgengine/magicsock/magicsock_test.go

@@ -453,7 +453,7 @@ func makeConfigs(t *testing.T, addrs []netaddr.IPPort) []wgcfg.Config {
 		privKeys = append(privKeys, wgkey.Private(privKey))
 
 		addresses = append(addresses, []netaddr.IPPrefix{
-			parseCIDR(t, fmt.Sprintf("1.0.0.%d/32", i+1)),
+			netaddr.MustParseIPPrefix(fmt.Sprintf("1.0.0.%d/32", i+1)),
 		})
 	}
 
@@ -481,15 +481,6 @@ func makeConfigs(t *testing.T, addrs []netaddr.IPPort) []wgcfg.Config {
 	return cfgs
 }
 
-func parseCIDR(t *testing.T, addr string) netaddr.IPPrefix {
-	t.Helper()
-	cidr, err := netaddr.ParseIPPrefix(addr)
-	if err != nil {
-		t.Fatal(err)
-	}
-	return cidr
-}
-
 // TestDeviceStartStop exercises the startup and shutdown logic of
 // wireguard-go, which is intimately intertwined with magicsock's own
 // lifecycle. We seem to be good at generating deadlocks here, so if