ip6mr: remove stray rcu_read_unlock() from ip6_mr_forward()

One rcu_read_unlock() should have been removed in blamed commit.

Fixes: 9b1c21d898fd ("ip6mr: do not acquire mrt_lock while calling ip6_mr_forward()")
Reported-by: Vladimir Oltean <[e-mail]>
Signed-off-by: Eric Dumazet <[e-mail]>
Reviewed-by: Vladimir Oltean <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/ipv6/ip6mr.c

···
 		 */
 		cache_proxy = mr_mfc_find_any_parent(mrt, vif);
 		if (cache_proxy &&
-		    cache_proxy->_c.mfc_un.res.ttls[true_vifi] < 255) {
-			rcu_read_unlock();
+		    cache_proxy->_c.mfc_un.res.ttls[true_vifi] < 255)
 			goto forward;
-		}
 	}
 
 	/*