Fix typo: side.bar.twig => sidebar.twig
bug #3509 Fix typo: side.bar.twig => sidebar.twig (ifdattic)

This PR was merged into the 2.3 branch.

Discussion
----------

Fix typo: side.bar.twig => sidebar.twig

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3
| Fixed tickets |

Commits
-------

3b142dd Fix typo: side.bar.twig => sidebar.twig