E3-593: Add missing variables on CONFIG_SITE_ENV
Remove EPICS_TIMEZONE that are just used for vxWorks, not used at ESS. This was replaced for the EPICS_TZ variable that should be defined for suppressing warnings.
The IOCSH_HISTEDIT_DISABLE variable was added on 3.16.0.1 and should be defined for suppressing warnings as we don't have use for it.