Update CONTRIBUTING.md

Repair link to Swift.org page.

CONTRIBUTING.md

@@ -1,6 +1,6 @@
 # Welcome to the Swift community! 
 
-Contributions to Swift are welcomed and encouraged! Please see the [Contributing to Swift guide](swift.org/contributing) and check out the [structure of the community](https://www.swift.org/community/#community-structure).
+Contributions to Swift are welcomed and encouraged! Please see the [Contributing to Swift guide](https://www.swift.org/contributing/) and check out the [structure of the community](https://www.swift.org/community/#community-structure).
 
 To be a truly great community, Swift needs to welcome developers from all walks of life, with different backgrounds, and with a wide range of experience. A diverse and friendly community will have more great ideas, more unique perspectives, and produce more great code. We will work diligently to make the Swift community welcoming to everyone.