Pkmn -> Mon

Since we're aiming for consistency across the codebase, I believe it
includes a uniform way to refer to the creatures this game consists of
in the labels of the code.
The only exceptions to this rule are labels referring to things named
through the use of the <PK><MN> or <PKMN> characters, in which case PKMN
is used.

Most of this was already consistent enough™, I just picked the
convention with the most occurences and fixed the outliers.

data/common_text/common_text_1.asm

@@ -1121,7 +1121,7 @@ Text_RemainingTime::
 	text "Remaining Time"
 	done
 
-Text_YourPkmnsHPWasHealed::
+Text_YourMonsHPWasHealed::
 	text "Your #MON's HP"
 	line "was healed."
 	prompt

data/common_text/common_text_2.asm

@@ -113,17 +113,17 @@ Text_StringBuffer2ExpPoints::
 	text " EXP. Points!"
 	prompt
 
-Text_GoPkmn::
+Text_GoMon::
 	text "Go! @@"
 
-Text_DoItPkmn::
+Text_DoItMon::
 	text "Do it! @@"
 
-Text_GoForItPkmn::
+Text_GoForItMon::
 	text "Go for it,"
 	line "@@"
 
-Text_YourFoesWeakGetmPkmn::
+Text_YourFoesWeakGetmMon::
 	text "Your foe's weak!"
 	line "Get'm, @@"
 
@@ -618,7 +618,7 @@ UnknownText_0x1c0bee::
 	cont "time to use that!"
 	prompt
 
-Text_YouDontHaveAPkmn::
+Text_YouDontHaveAMon::
 	text "You don't have a"
 	line "#MON!"
 	prompt

data/common_text/common_text_3.asm

@@ -1139,14 +1139,14 @@ UnknownText_0x1c59a3::
 	para ""
 	done
 
-Text_OnlyThreePkmnMayBeEntered::
+Text_OnlyThreeMonMayBeEntered::
 	text "Only three #MON"
 	line "may be entered."
 
 	para ""
 	done
 
-Text_ThePkmnMustAllBeDifferentKinds::
+Text_TheMonMustAllBeDifferentKinds::
 	text "The @"
 	text_from_ram wStringBuffer2
 	text " #MON"
@@ -1156,7 +1156,7 @@ Text_ThePkmnMustAllBeDifferentKinds::
 	para ""
 	done
 
-Text_ThePkmnMustNotHoldTheSameItems::
+Text_TheMonMustNotHoldTheSameItems::
 	text "The @"
 	text_from_ram wStringBuffer2
 	text " #MON"