Replaced broken link to the "Translations" page :) (napari#7243)

# References and relevant issues
None.

# Description
Replacing broken link to the "Translations" page in
PULL_REQUEST_TEMPLATE.md.

.github/PULL_REQUEST_TEMPLATE.md

@@ -15,5 +15,5 @@ a screenshot or a screen capture: "An image is worth a thousand words!" -->
   (open a PR on the docs repository (https://github.com/napari/docs) if relevant!)
 - I have added tests that prove my fix is effective or that my feature works
 - If I included new strings, I have used `trans._("some string")` to make them localizable.
-  (For more information see our [translations guide](https://napari.org/developers/translations.html)).
+  (For more information see our [translations guide](https://napari.org/stable/developers/contributing/translations.html)).
 -->