Fix rst syntax error in PROJECTS.rst.

Thanks: @tahadnan

Author: jonathanslenders

Diff for: PROJECTS.rst

@@ -52,7 +52,7 @@ Full screen applications:
 - `sanctuary-zero <https://github.com/t0xic0der/sanctuary-zero>`_: A secure chatroom with zero logging and total transience.
 - `Hummingbot <https://github.com/CoinAlpha/hummingbot>`_: A Cryptocurrency Algorithmic Trading Platform
 - `git-bbb <https://github.com/MrMino/git-bbb>`_: A `git blame` browser.
-- `ass <https://github.com/mlang/ass`_: An OpenAI Assistants API client.
+- `ass <https://github.com/mlang/ass>`_: An OpenAI Assistants API client.
 
 Libraries: