Remove unused RBASIC_RESET_FLAGS #276

Job	Run time
make (check, --enable-yjit, --yjit)	7m 12s
cargo test	43s
make (check, --enable-yjit=dev, --yjit-call-threshold=1 --yjit-verify-ctx --yjit-code-gc, -T --yj...	18m 37s
YJIT macOS Arm64 result	3s
	26m 35s

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