Adjust sleep spell, and monk starting spell

Tone down sleep level to 3 (hitting a monster does tend to wake
it up), and replace the random monk starting sleep spell with
confuse monster, which fits nicely with monk's bare-handed
fighting style.

doc/fixes3-7-0.txt

@@ -801,6 +801,7 @@ always give a message when monster changes form via polytrap if seen
 illiterate hero receiving a spellbook from their deity gets the spell shoved
 	directly into their mind instead
 adjust levels of sleep, confuse monster, and charm monster spells
+replace monk starting sleep spell with confuse monster
 chargeable rings have a chance of getting charged when hit with electricity