Makes the spelling of 'mjollnir' consistant and renames singularityhammer.dm to wizard_weapons.dm 2 (#79700)

## About The Pull Request

All the below copied from #79588 

Does as the tin says and renames all instances of 'mjolnir' to
'mjollnir' . They are TECHNICALLY both correct but because 'mjolnir' was
only used for the spelling in game for the hammer itself and the icon
when worn on the back I decided on two l's. This also means I had to
change the icon name for the back sprite

If I'm missing any files with it spelt 'mjolnir' please tell me

While I was at it i also decided to change singularityhammer.dm to
wizard_weapons.dm because apparently the file is supposed to be where
wizard weapon are stored and having it be named after a single weapon is
confusing incase people add more weapons later on.




## Why It's Good For The Game
More consistent spelling.

Code wise it makes it more clear what the intended use for a file is
 

## Changelog
🆑
spellcheck: hopefully changed all instances of the word 'mjolnir' to
'mjollnir'
/🆑

code/game/objects/items/wizard_weapons.dm

@@ -77,12 +77,12 @@
 	return .
 
 /obj/item/mjollnir
-	name = "Mjolnir"
+	name = "Mjollnir"
 	desc = "A weapon worthy of a god, able to strike with the force of a lightning bolt. It crackles with barely contained energy."
 	icon = 'icons/obj/weapons/hammer.dmi'
 	icon_state = "mjollnir0"
 	base_icon_state = "mjollnir"
-	worn_icon_state = "mjolnir"
+	worn_icon_state = "mjollnir"
 	lefthand_file = 'icons/mob/inhands/weapons/hammers_lefthand.dmi'
 	righthand_file = 'icons/mob/inhands/weapons/hammers_righthand.dmi'
 	flags_1 = CONDUCT_1

tgstation.dme

@@ -2227,7 +2227,6 @@
 #include "code\game\objects\items\shooting_range.dm"
 #include "code\game\objects\items\shrapnel.dm"
 #include "code\game\objects\items\signs.dm"
-#include "code\game\objects\items\singularityhammer.dm"
 #include "code\game\objects\items\skub.dm"
 #include "code\game\objects\items\spear.dm"
 #include "code\game\objects\items\sticker.dm"
@@ -2247,6 +2246,7 @@
 #include "code\game\objects\items\wall_mounted.dm"
 #include "code\game\objects\items\weaponry.dm"
 #include "code\game\objects\items\wiki_manuals.dm"
+#include "code\game\objects\items\wizard_weapons.dm"
 #include "code\game\objects\items\AI_modules\_AI_modules.dm"
 #include "code\game\objects\items\AI_modules\freeform.dm"
 #include "code\game\objects\items\AI_modules\full_lawsets.dm"