Fixed broken link to external libraries.

raylib-architecture.md

@@ -27,8 +27,6 @@ Most of the secondary modules (`raymath`, `camera`, `gestures`, `raygui`, `easin
 
 NOTE: *The `raymath`, `camera` and `gestures` modules are all compiled with raylib by default.*
 
-raylib also uses some external libraries (most of which are included as single-file, header-only libraries), including the well known [stb libraries](https://github.com/nothings/stb) and [some other similar libraries](https://github.com/raysan5/raylib/tree/develop/src/external).
+raylib also uses some external libraries (most of which are included as single-file, header-only libraries), including the well known [stb libraries](https://github.com/nothings/stb) and [some other similar libraries](https://github.com/raysan5/raylib/tree/master/src/external).
 
-Familiarity with the modules is essential for raylib proficiency. Refer to [the Cheatsheet][1] for a comprehensive summary.
-
-[1]: https://www.raylib.com/cheatsheet/cheatsheet.html
+Familiarity with the modules is essential for raylib proficiency. Refer to [the Cheatsheet](https://www.raylib.com/cheatsheet/cheatsheet.html) for a comprehensive summary.