Use UMASK syscall instead of AFS_SYSCALL in seccomp test.
Use UMASK syscall instead of AFS_SYSCALL in seccomp test.

AFS_SYSCALL is not defined on ARM which causes nogo
tests to fail when they land on ARM machines.

I don't think umask(2) is being called by go runtime
or any instrumentation, otherwise the test would be
failing because it doesn't exist in filters.

PiperOrigin-RevId: 454037751

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