Bump httpx from 0.16.1 to 0.17.1 (#288)

Bumps [httpx](https://github.com/encode/httpx) from 0.16.1 to 0.17.1.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.16.1...0.17.1)

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

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

requirements.txt

@@ -1,3 +1,3 @@
 Click==7.1.2
-httpx==0.16.1
+httpx==0.17.1
 attrs==20.3.0