Fix feature request guidelines link in discussion template (#49129)

Seems like a small oversight, or rather, we didn’t have this discussion
at that point? Either way @JosephTLyons feel free to merge once you
confirm this is the intended URL.

Closes #49119.

Release Notes:

- N/A

.github/DISCUSSION_TEMPLATE/feature-requests.yml

@@ -40,4 +40,4 @@ body:
     attributes:
       value: |
         Learn more about how feature requests work in our
-        [Feature Request Guidelines](LINK_TO_GUIDE_HERE).
+        [Feature Request Guidelines](https://github.com/zed-industries/zed/discussions/47963).