Fix a typo in macos.md [skip ci]
Fix a typo in macos.md [skip ci]


Former-commit-id: a74c6e64d3086e9aefe9adfeb2879e289efd21de [formerly 137b3bd3bafe429dcd5bad82bd782e2064d5a955]
Former-commit-id: b59e9cdf233a3691bb7600d7221487b9855ca5a7
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine