Update httpcore requirement from <0.17.0,>=0.15.0 to >=0.15.0,<0.18.0 (#2642)

Updates the requirements on [httpcore](https://github.com/encode/httpcore) to permit the latest version.
- [Release notes](https://github.com/encode/httpcore/releases)
- [Changelog](https://github.com/encode/httpcore/blob/master/CHANGELOG.md)
- [Commits](encode/httpcore@0.15.0...0.17.0)

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

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

Author: dependabot[bot]

pyproject.toml

@@ -29,7 +29,7 @@ classifiers = [
 ]
 dependencies = [
     "certifi",
-    "httpcore>=0.15.0,<0.17.0",
+    "httpcore>=0.15.0,<0.18.0",
     "idna",
     "sniffio",
 ]