IRQs and sharing was an issue of the hardware bus design (ISA, EISA, MCA, PCI, etc.). ISA didn’t support it since it is an “edge triggered interrupt” but newer hardware architectures (as well as MCA, Microchannel, which is not so new) do support it because of the explosion in devices that need to be supported on a single motherboard now.
That’s just in case you’re curious.
Like others said, leave it alone. It doesn’t cause problems now.