[3.6] Bump aiohttp-theme from 0.1.5 to 0.1.6 (#4210)

Bumps [aiohttp-theme](https://github.com/aio-libs/aiohttp-theme) from 0.1.5 to 0.1.6.
- [Release notes](https://github.com/aio-libs/aiohttp-theme/releases)
- [Changelog](https://github.com/aio-libs/aiohttp-theme/blob/master/docs/changelog.rst)
- [Commits](aio-libs/aiohttp-theme@v0.1.5...v0.1.6)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

requirements/doc.txt

@@ -1,5 +1,5 @@
 sphinx==2.2.0
 sphinxcontrib-asyncio==0.2.0
 pygments==2.4.2
-aiohttp-theme==0.1.5
+aiohttp-theme==0.1.6
 sphinxcontrib-blockdiag==1.5.5