Bump aiohttp from 3.7.4 to 3.8.5 in /examples/server/aiohttp

Bumps [aiohttp](https://github.com/aio-libs/aiohttp) from 3.7.4 to 3.8.5.
- [Release notes](https://github.com/aio-libs/aiohttp/releases)
- [Changelog](https://github.com/aio-libs/aiohttp/blob/v3.8.5/CHANGES.rst)
- [Commits](https://github.com/aio-libs/aiohttp/compare/v3.7.4...v3.8.5)

---
updated-dependencies:
- dependency-name: aiohttp
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

examples/server/aiohttp/requirements.txt

@@ -1,4 +1,4 @@
-aiohttp==3.7.4
+aiohttp==3.8.5
 async-timeout==1.1.0
 chardet==2.3.0
 multidict==2.1.4