Don't erase Elbereth when monster steps into a pit or hole dug by you

Elbereth was fading when offscreen monsters stepped into
pits or holes dug elsewhere on the level. This was happening
because monsters falling into traps set by you were calling
setmangry() as if you had just attacked them. The behavior
made it unsafe to use Elbereth if you've dug down anywhere
else on the level, making it a bit harder to get archeologists
off the ground.

src/trap.c

@@ -3117,7 +3117,7 @@ mintrap(register struct monst *mtmp)
            Recognizing who made the trap isn't completely
            unreasonable; everybody has their own style. */
         if (trap->madeby_u && rnl(5))
-            setmangry(mtmp, TRUE);
+            setmangry(mtmp, FALSE);
 
         return trapeffect_selector(mtmp, trap, 0);
     }