Bump httpx from 0.15.5 to 0.16.0

Bumps [httpx](https://github.com/encode/httpx) from 0.15.5 to 0.16.0.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.15.5...0.16.0)

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

Author: dependabot-preview[bot]

poetry.lock

@@ -32,7 +32,7 @@ importlib_metadata = {version = "^2.0.0", python = "<3.8"}
 pydantic = "^1.6.1"
 attrs = "^20.1.0"
 python-dateutil = "^2.8.1"
-httpx = "^0.15.4"
+httpx = ">=0.15.4,<0.17.0"
 autoflake = "^1.4"
 
 [tool.poetry.scripts]