use sudoedit in Whonix documentation and Whonix software

[Patrick]

@Patrick_mobile

That is because https://help.ubuntu.com/community/RootSudo contradicts it and says

gksu has been replaced by pkexec, but even pkexec is being deprecated by the mainline Ubuntu developers. They have taken the position that file manipulation and editing under root should be restricted to the command line.

Also citation required.

Very much citation required since RootSudo - Community Help Wiki also says:

March 14, 2019 PLEASE NOTE: This wiki article is being significanly rewritten as it contains a good deal of old, dated and possibly questionable material. Using caution and consulting with others on the Ubuntu Forums or Ask Ubuntu is highly recommended!