Remove not necessary changelog about time zone array mutation

This seemed to be introduced in master by
9dd64f2e0c1b3ce85b503b0f81c50c93f89ffbcd, so there's no need to add a
changelog entry for fixing it.

[ci skip]
Fix test name and refactor fake timezones creation in form options test
Use Array Difference to calculate the zones array, instead of iterating

It's faster, and doesn't force us to dup the timezones array.
Use #grep to filter priority zones when a regexp is given