Revert "tailcfg, controlclient, magicsock: request IPv6 endpoints, but ignore them"

Breaks something deep in wireguard or magicsock's brainstem, no packets at all
can flow. All received packets fail decryption with "invalid mac1".

This reverts commit 94024355ed.

Signed-off-by: David Anderson <dave@natulte.net>

wgengine/magicsock/magicsock.go

@@ -1456,10 +1456,6 @@ func (c *Conn) CreateEndpoint(key [32]byte, addrs string) (conn.Endpoint, error)
 			}
 			if ip4 := addr.IP.To4(); ip4 != nil {
 				addr.IP = ip4
-			} else {
-				// TODO(bradfitz): stop skipping IPv6 ones for now.
-				c.logf("magicsock: CreateEndpoint: ignoring IPv6 addr %v for now", addr)
-				continue
 			}
 			a.addrs = append(a.addrs, *addr)
 		}