Remove stray apostrophe in README (#126)

Just fixes a tiny grammatical error in the README.

Co-authored-by: Eric Wagoner <ewagoner@gmail.com>
Reviewed-on: https://gitea.com/gitea/awesome-gitea/pulls/126
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: John Olheiser <john+gitea@jolheiser.com>
Co-authored-by: ewagoner <ewagoner@noreply.gitea.com>
Co-committed-by: ewagoner <ewagoner@noreply.gitea.com>

README.md

@@ -3,7 +3,7 @@
 [![Awesome](https://awesome.re/badge-flat.svg)](https://awesome.re)
 [![Contribution%20Guide](https://img.shields.io/badge/-Contribution%20Guide-informational?style=flat)](contributing.md)
 
-A curated list of awesome projects related to Gitea and it's soft-fork instances.
+A curated list of awesome projects related to Gitea and its soft-fork instances.
 
 ## Contents