Use UTF-8 instead of UTF-16 BOM LE formatting for maps

[vtcifer]

Currently, genie will READ UTF-8 xml for maps, but will not write it out when saving from the UI. We need to convert it prior to commit to git, or git complains the file format.

I'm pretty sure this is the line that needs changing:

Genie4/Mapper/MapForm.cs

Line 919 in f41a5a8

var xw = new XmlTextWriter(sPath, System.Text.Encoding.Unicode);

and we just need to tell instead of System.Text.Encoding.Unicode to use System.Text.Encoding.UTF8 or null

https://learn.microsoft.com/en-us/dotnet/api/system.xml.xmltextwriter.-ctor?view=net-8.0#system-xml-xmltextwriter-ctor(system-string-system-text-encoding)