update vkquake submodule #600

Job	Run time
quakespasm - Linux Clang	47s
quakespasm - Linux GCC	35s
quakespasm - macOS Intel	49s
quakespasm - macOS ARM	36s
quakespasm - MSVC 32-bit	36s
quakespasm - MSVC 64-bit	1m 1s
quakespasm-spiked - Linux Clang	57s
quakespasm-spiked - Linux GCC	48s
quakespasm-spiked - macOS Intel	1m 22s
quakespasm-spiked - macOS ARM	35s
quakespasm-spiked - MSVC 32-bit	1m 4s
quakespasm-spiked - MSVC 64-bit	1m 25s
vkquake - Linux Clang	55s
vkquake - Linux GCC	56s
vkquake - macOS Intel	1m 26s
vkquake - macOS ARM	52s
vkquake - MSVC 32-bit	1m 25s
vkquake - MSVC 64-bit	1m 16s
ironwail - Linux Clang	54s
ironwail - Linux GCC	1m 3s
ironwail - macOS Intel	1m 13s
ironwail - macOS ARM	34s
ironwail - MSVC 32-bit	1m 4s
ironwail - MSVC 64-bit	1m 5s
	23m 18s

Provide feedback