The Repeat Zone operator from the Geometry nodes Add Node -> Utilities
menu was not translated because it used the "Operator" translation
context, instead of the default context.
Since the function displaying the menu item, `add_repeat_zone()`, is
only ever called from the Utilities menu, and the label is specified
there as "Repeat Zone", we know in advance that it will have this
name.
For the same reason, this commit also simplifies the function which
creates the menu entry for simulation zones. This function is also
only called from the Simulation menu with a specific label using the
default context, so it should also use this one.
