mention_decor vs Underwater or drowning escape

Avoid redundant
|You are on solid land again.
|You are back on floor.
when walking or teleporting out of water with the mention_decor option on.

src/trap.c

@@ -5361,6 +5361,7 @@ lava_effects()
             pline("You're still burning.");
         }
         You("find yourself back on solid %s.", surface(u.ux, u.uy));
+        iflags.last_msg = PLNMSG_BACK_ON_GROUND;
         return TRUE;
     } else if (!Wwalking && (!u.utrap || u.utraptype != TT_LAVA)) {
         boil_away = !Fire_resistance;