Remove unused RBASIC_RESET_FLAGS #13

Job	Run time
make (ruby, --enable-yjit --enable-zjit)	3m 30s
make (zjit-test, --enable-yjit=dev --enable-zjit)	3m 39s
make (test-all, --enable-zjit=dev, ../src/test/ruby/test_zjit.rb)	3m 12s
ZJIT macOS Arm64 result	3s
	10m 24s

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