Changed portable generator sheet burn times (#2882)

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## About The Pull Request

Portable generators all have different burn times. This unifies them.

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## Why It's Good For The Game

The superpacman was actually inferior, and considerably so, to the
regular pacman in total energy generated. A pacman had a time_per_sheet
of 260, while a superpacman was only 85 for only double the power! This
made it inferior in every way, because uranium is also quite rare.

While there are no obtainable mrspacmans as far as I am aware, I find no
reason to have any of these generators set with different burn times.
This simplifies it by unifying all of them into the same base
time_per_sheet of 260.

I am aware this is going to mess with balance a little bit, but I
believe that simplifying the amount of variables in play will help make
balancing easier in the long run, because it isn't immediately obvious
that there were different sheet burn times. Balance should be affected
by changing power generated, uranium spawn rate, number of sheets and
generators at round start... etc, not some property that you can't see
unless you stand there comparing generators side by side.

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## Changelog

:cl:
tweak: All pacman and its variants now have the same sheet burn times.
Superpacmans are no longer the vastly inferior generator.
/:cl:

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Co-authored-by: FalloutFalcon <[email protected]>

code/modules/power/port_gen.dm

@@ -291,7 +291,6 @@
 	circuit = /obj/item/circuitboard/machine/pacman/super
 	sheet_path = /obj/item/stack/sheet/mineral/uranium
 	power_gen = 15000
-	time_per_sheet = 85
 
 /obj/machinery/power/port_gen/pacman/super/overheat()
 	. =..()
@@ -304,7 +303,6 @@
 	circuit = /obj/item/circuitboard/machine/pacman/mrs
 	sheet_path = /obj/item/stack/sheet/mineral/diamond
 	power_gen = 40000
-	time_per_sheet = 80
 
 /obj/machinery/power/port_gen/pacman/mrs/overheat()
 	. =..()