wgengine/magicsock: fix Conn docs type reference

The docs on magicsock.Conn stated that they implemented the
wireguard/device.Bind interface, yet this type does not exist. In
reality, the Conn type implements the wireguard/conn.Bind interface.

I also fixed a small typo in the same file.

Signed-off-by: Blake Gentry <blakesgentry@gmail.com>

wgengine/magicsock/magicsock.go

@@ -46,7 +46,7 @@ import (
 )
 
 // A Conn routes UDP packets and actively manages a list of its endpoints.
-// It implements wireguard/device.Bind.
+// It implements wireguard/conn.Bind.
 type Conn struct {
 	pconnPort    uint16 // the preferred port from opts.Port; 0 means auto
 	pconn4       *RebindingUDPConn
@@ -1514,7 +1514,7 @@ type AddrSet struct {
 	// stopSpray is the time after which we stop spraying packets.
 	stopSpray time.Time
 
-	// lastSpray is the lsat time we sprayed a packet.
+	// lastSpray is the last time we sprayed a packet.
 	lastSpray time.Time
 }