Remove clang-18 from compilers CI #58

Job	Run time
cargo clippy	38s
ruby-bench (--zjit-call-threshold=2, --warmup=1 --bench=1, --enable-zjit=dev_nodebug)	20m 28s
make (check, --zjit-call-threshold=1, -T --zjit-call-threshold=1, --enable-zjit=dev)	19m 13s
make (check, --zjit-disable-hir-opt --zjit-call-threshold=1, -T --zjit-disable-hir-opt -T --zjit-...	15m 37s
make (zjit-check, --enable-yjit --enable-zjit=dev, 1.85.0)	4m 46s
make (zjit-bindgen, To fix: use patch in logs, --enable-zjit=dev --with-gcc=clang-16, /usr/bin/cl...	4m 55s
make (test-bundled-gems, --enable-zjit=dev, --zjit-call-threshold=1)	21m 31s
ZJIT Ubuntu result	2s
	1h 27m 10s

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