Update PULL_REQUEST_TEMPLATE.md

Author: gaborbernat

.github/PULL_REQUEST_TEMPLATE.md

@@ -15,8 +15,8 @@ much about the checklist - we will help you get started.
 - [ ] added news fragment in [changelog folder](/docs/changelog)
   * fragment name: `<issue number>.<type>.rst` for example (588.bugfix.rst)
   * `<type>` is must be one of `bugfix`, `feature`, `deprecation`,`breaking`, `doc`, `misc`
-  * if pr has no issue: consider creating one first or change it to the pr number after creating the pr
-  * "sign" fragment with "by @<your username>"
+  * if PR has no issue: consider creating one first or change it to the PR number after creating the PR
+  * "sign" fragment with "by :user:`<your username>`"
   * please use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files - by :user:`superuser`."
   * also see [examples](/docs/changelog/examples.rst)
 - [ ] added yourself to `CONTRIBUTORS` (preserving alphabetical order)