Fix README links (#11382)

This PR fixes the links in the README to account for the changes in the
docs structure.

Also, somehow the README had gotten added with `\r\n` newlines, so I
changed it back to `\n` newlines.

Release Notes:

- N/A

docs/src/development/local-collaboration.md

@@ -1,6 +1,6 @@
 # Local Collaboration
 
-First, make sure you've installed Zed's [backend dependencies](./developing_zed__building_zed.md#backend-dependencies).
+First, make sure you've installed Zed's [backend dependencies](../developing-zed.md#backend-dependencies).
 
 ## Database setup