tests: Remove tests requiring comp of novel ISAs in long

The only tests requiring the the compilation of SPARC, MIPS, and POWER
for the long/nightly suite were
"tests/gem5/multi_isa/test_multi_isa.py" and
"gem5/stdlib/test_requires.py". As compilation of gem5 is quite costly,
it'd best we simply remove these tests. They are minor and not very

Compilation of these ISAs will continue to be tested via the compilation

Change-Id: I98b33eec5d0adb144109d32851033380f1641ad4
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/65193
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed