fix(pr-template) update broken reference in PR template

.github/pull_request_template.md

@@ -8,7 +8,7 @@ Fixes [list issues/bugs if needed]
 
 1. Run the LXD-UI:
     - On the demo server via the link posted by @webteam-app below. This is only available for PRs created by collaborators of the repo. Ask @lorumic or @edlerd for access.
-    - With a local copy of this branch, run as described in the [Readme](https://github.com/canonical/lxd-ui#setting-up-for-development).
+    - With a local copy of this branch, run as described [here](../HACKING.md#setting-up-for-development).
 2. Perform the following QA steps:
     - [List the steps to QA the new feature(s) or prove that a bug has been resolved]