Fix typo in "FarmdData2"

[wpgoble]

In the paragraph under the "Bug Fix / Feature Implementation" heading in CONTRIBUTING.md, the word "FarmData2" contains an extra "d" that should be removed.

[DSonBuss]

I would like to work on this please!

[github-actions]

Great! I assigned you (@DSonBuss) to the issue. Have fun working on it!