Updated hyperlinks for Issues(line 33) and Pull Requests(line 34) (#31696)

Summary:
In the CONTRIBUTING.md file, when a user clicks on the hyperlink for either issues(line 33) or pull requests(line 34), they are directed to a filler page which has them click on an additional hyperlink to take them to the page they are looking for. The only thing present on the filler page is a hyperlink. So, in terms of usability, it does not make sense to have users go through an extra click to get to the page they want. I have changed the hyperlinks of Issues(line 33) and Pull Requests(line 34) to takes users directly to Triaging GitHub Issues and Managing-Pull-Requests

## Changelog

[GENERAL][CHANGED]-See lines 33 and 34 of https://github.com/facebook/react-native/blob/master/CONTRIBUTING.md

Pull Request resolved: https://github.com/facebook/react-native/pull/31696

Test Plan: First, I ensured that the code lints and the test suite passes. For testing the links, I opened my fork in GitHub and opened the CONTRIBUTING.md file. I clicked on both hyperlinks to ensure that they both worked properly. No tests were added for this code.

Reviewed By: lunaleaps

Differential Revision: D29046728

Pulled By: TheSavior

fbshipit-source-id: 99ec989938660102aefa07862542dc9a007359ce