Remove Siren REPAIR category

[Hdt80bro]

Currently, the Siren Class cruiser has the REPAIR category - presumably because it's an air staging platform that can repair aircraft. What this actually does is let it repair other units like an engineer, despite having no visual indication or defined build rate - it defaults to 1 and is incredibly slow. If this was intended, it would have been more clear with an appreciable build rate and effect (maybe even an animation, unit description line, or unit ability), but given the context, it appears to be a simple oversight.

Notice the orange progress bar and 1 power drain - the damaged cruiser used to be at 30% health but is now at 32%

[lL1l1]

That's an old screenshot; units with an undefined buildrate are postprocessed to 0.

fa/lua/system/blueprints-units.lua

Lines 537 to 541 in 2e38df9

	-- Override the default 1 build rate given to units
	-- so that rollover unit view can work with Mantis.
	if unit.Economy and not unit.Economy.BuildRate then
	unit.Economy.BuildRate = 0
	end

Even with 0 buildrate the Siren still tries to repair, not moving into formation and displaying the work progress bar, so it's good to remove the category for that reason too.