A couple of bug fixes

More still need to be done but I'm separating the commits so I don't get overwhelmed lol

- Fixes a bug with the Up-Grade NPC in Saffron. He now properly shows up only after defeating Giovanni.

- Fixes a bug where Silph could be entered before receiving the Poke Flute.

- Silph Gauntlet 5F has a complete remodel, more closely matching the original map found in the leaks.

- One of the Fuchsia Gym Trainers no longer uses a repeat Arbok.

- Wiglett and Wugtrio could learn Rock Slide via TM, which has now been fixed.

- Jacky uses a Porygon in place of Machop, as it ties into his polygonal, Virtua Fighter-inspired sprite.

- Chief uses a Gengar instead of Porygon2 to represent the Silph Scope.

- Omega's and Giovanni 2's levels have been toned down slightly.

- Lance now uses Crocky over Aerodactyl.

- Yujirou's non-initial teams have had their levels reduced to be the same level as the previously-fought Gym Leader, rather than the upcoming one.

- Updated README with additional credits.

constants/hide_show_constants.asm

@@ -37,8 +37,7 @@ DEF SHOW EQU $15
 	const HS_SAFFRON_CITY_D                ; 16
 	const HS_SAFFRON_CITY_E                ; 17
 	const HS_SAFFRON_CITY_F                ; 18
-	const HS_SAFFRON_CITY_UP_GRADE         ; 19
-	const HS_ROUTE_1_OAK                   ; F0
+	const HS_ROUTE_1_OAK                   ; 19
 	const HS_ROUTE_2_ITEM_1                ; 1A X
 	const HS_ROUTE_2_ITEM_2                ; 1B X
 	const HS_ROUTE_4_ITEM                  ; 1C X