Fix link in PR template

Author: hugovk

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,7 @@
 ## Description
 
 Thanks for contributing to tskit! :heart:
-A guide to the PR process is [here](https://tskit.readthedocs.io/en/latest/development.html#development_workflow_git)
+A guide to the PR process is [here](https://tskit.dev/tskit/docs/stable/development.html#git-workflow)
 Please replace this text with a summary of the change and which issue is fixed, if any. Please also include relevant motivation and context.
 
 Fixes #(issue) <- Putting the issue number here will auto-close the issue when this PR is merged