Remove $wgHttpOnlyBlacklist

This hack was added in r34083 / 6b16f4410897 to support IE for Mac.
That browser is no longer supported, and no additional user-agent
strings have been added in WMF configuration.

Change-Id: Iffba121a9964e2ad387fad8827ddfd8dabcbd12e
Merge "Remove $wgHttpOnlyBlacklist"