fix docs: update broken links and edit for conciseness (ray-project#3…

…2733)

Signed-off-by: David Xia <dxia@spotify.com>

CONTRIBUTING.rst

@@ -13,16 +13,15 @@ You can post questions or issues or feedback through the following channels:
 To contribute a patch:
 ----------------------
 
-We welcome your contribution!  Please see https://docs.ray.io/en/master/getting-involved.html for instructions.
-
-For instructions on setting up your development environment, check out the
-`getting involved`_ documentation page.
+We welcome contributions! See `Getting Involved`_. To set up your development environment, see
+the `Setting up your development environment`_ section.
 
 
 .. _`Discourse forum`: https://discuss.ray.io/
 .. _`GitHub Issues`: https://github.com/ray-project/ray/issues
 .. _`StackOverflow`: https://stackoverflow.com/questions/tagged/ray
-.. _`getting involved`: https://docs.ray.io/en/master/getting-involved.html
+.. _`Getting Involved`: https://docs.ray.io/en/latest/ray-contribute/getting-involved.html
+.. _`Setting up your development environment`: https://docs.ray.io/en/latest/ray-contribute/getting-involved.html#setting-up-your-development-environment
 
 PR Review Process
 -----------------