Bump starlette from 0.37.2 to 0.38.4

Bumps [starlette](https://github.com/encode/starlette) from 0.37.2 to 0.38.4.
- [Release notes](https://github.com/encode/starlette/releases)
- [Changelog](https://github.com/encode/starlette/blob/master/docs/release-notes.md)
- [Commits](encode/starlette@0.37.2...0.38.4)

---
updated-dependencies:
- dependency-name: starlette
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

poetry.lock

@@ -65,7 +65,7 @@ django = {version = ">=3.0", optional = true}
 falcon = {version = ">=3.0", optional = true}
 flask = {version = "*", optional = true}
 aiohttp = {version = ">=3.0", optional = true}
-starlette = {version = ">=0.26.1,<0.38.0", optional = true}
+starlette = {version = ">=0.26.1,<0.39.0", optional = true}
 isodate = "*"
 more-itertools = "*"
 parse = "*"
@@ -101,7 +101,7 @@ pytest-flake8 = "*"
 pytest-cov = "*"
 python-multipart = "*"
 responses = "*"
-starlette = ">=0.26.1,<0.38.0"
+starlette = ">=0.26.1,<0.39.0"
 strict-rfc3339 = "^0.7"
 webob = "*"
 mypy = "^1.2"