build(deps): update ansible-core requirement from <2.15,>=2.13 to >=2…

….13,<2.16 in /docs (#134)

build(deps): update ansible-core requirement in /docs

Updates the requirements on [ansible-core](https://github.com/ansible/ansible) to permit the latest version.
- [Release notes](https://github.com/ansible/ansible/releases)
- [Commits](ansible/ansible@v2.13.0...v2.15.0)

---
updated-dependencies:
- dependency-name: ansible-core
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/requirements.txt

@@ -2,7 +2,7 @@
 # GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-ansible-core>=2.13,<2.15
+ansible-core>=2.13,<2.16
 antsibull-docs >= 1.0.0, < 3.0.0
 ansible-pygments
 sphinx