base: Remove SYSLOG* macros from logging.h.
base: Remove SYSLOG* macros from logging.h.

They are unused and are equivalent to the LOG* macros anyhow.

Review URL: https://codereview.chromium.org/1602293002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#370295}

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