The Vilna edition, is 19th century.
The first censored edition may be the Vilna.
The Vilna edition has a reason to be censored, that being, it was written pre emancipation. Many modern publications unfortunately use the Vilna edition hebrew, which is censored.
And further info on censored editions or manuscripts, is mentioned in Rav Shabse Frankel's edition.
Some further info below- which at least elaborates a bit and may to an extent, point in the right direction of an answer
Of The Moznaim edition (this is the one translated by Rabbi Eliyahu Touger and available on chabad.org)
http://dev.ronware.org/p/targum/home mentions regarding translations..(and he comments on the censored hebrew too).
That link says of it "the Hebrew text is based on the censored (and otherwise inaccurate) Vilna printed editions. In addition, the translation is often inaccurate (straying even from the poor source text used!) and incorrect.").
I notice it translates bnai noach as gentile.
Ron mentions there's a Yale edition translation, though not sure what source text it uses so can't comment on whether that source is censored.
And he mentions a Birnbaum edition which only has what the author thought were highlights. Noach(of this thread/mi yodea/judaism.stackexchange), points out in comment that the Birnbaum edition, is 20th century.
Mechon Mamre says similarly to Ron of ronware.. http://www.mechon-mamre.org/p/index.htm "popular printed version of Mishneh Torah generally photocopied from the old Vilna version, which is generally used in almost all houses of study and Jewish homes despite that it is not at all an accurate text." and " We have noted with horror the corrupt Hebrew text underlying some of the popular English translations widely available today. We have also been disappointed by the quality of the translation, even of those based on a good Hebrew text; while they are generally written in good English, their content is often hardly parallel to the Hebrew supposedly translated, and sometimes it is the very opposite of the Hebrew. "
I have found there is a publication by Friedberg which may have been done post 2000, but uses a censored text. As we see in hilchot avoda zara 9:4 http://hebrewbooks.org/rambam.aspx?sefer=1&hilchos=4&perek=9&halocha=4&hilite=
and in hilchot melachim 10:9 http://hebrewbooks.org/rambam.aspx?sefer=14&hilchos=83&perek=10&halocha=9&hilite=
I would guess that Friedberg (which - as seen - is censored), is using the same censored source as Moznaim, And Ron of the Ronware link, says that Moznaim's source text is a censored Vilna edition.
Perhaps it's the Vilna edition that is the "original"/first censored text, or perhaps just the first text with censoring that was a complete published text?
mentions an edition by Rav Shabse Frankel that contains "thousands of fine notes on changes in the text between the manuscripts and the printed versions at the end of each volume of the excellent set edited by the Rav Shabse Frankel (and especially his introductory notes on this matter at the start of volume 2)..........Frankel does not bring the correct text "inside" but in his end notes only."