Remove unused BROWSER_TEXT_SIZE_CHANGE log event.

It turns out that the BROWSER_TEXT_SIZE_CHANGE event isn't listed
in google3/wireless/android/production/checkin_config/root,
which means that statistics on it isn't collected, so the logging
statement doesn't have any useful effect and can be removed to
simplify code.

Change-Id: I66d694cdb13e677bb979f5e962ed2cc8d743bdec