docs: add kb on how to manually update keyman for windows when automatic upgrade doesn't work

[rc-swag]

[rc-swag]

This is no longer needed due to the changes made with issue keymanapp/keyman#14536
See also:

• bug(windows): automatic update from 18.0.202 to 18.0.235 failed due to two keyman-x.y.z.exe in UpdateCache folder keyman#13831
• feat: add check for 18.0.235 and 18.0.236 releases and return the url for a special fix update to 18.0.239 or later api.keyman.com#293