Bump httpx from 0.27.2 to 0.28.0 in /requirements

Bumps [httpx](https://github.com/encode/httpx) from 0.27.2 to 0.28.0.
- [Release notes](https://github.com/encode/httpx/releases)
- [Changelog](https://github.com/encode/httpx/blob/master/CHANGELOG.md)
- [Commits](encode/httpx@0.27.2...0.28.0)

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

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

requirements/main.txt

@@ -186,9 +186,9 @@ httptools==0.6.4 \
     --hash=sha256:f9eb89ecf8b290f2e293325c646a211ff1c2493222798bb80a530c5e7502494f \
     --hash=sha256:fc411e1c0a7dcd2f902c7c48cf079947a7e65b5485dea9decb82b9105ca71a43
     # via uvicorn
-httpx==0.27.2 \
-    --hash=sha256:7bb2708e112d8fdd7829cd4243970f0c223274051cb35ee80c03301ee29a3df0 \
-    --hash=sha256:f7c2be1d2f3c3c3160d441802406b206c2b76f5947b11115e6df10c6c65e66c2
+httpx==0.28.0 \
+    --hash=sha256:0858d3bab51ba7e386637f22a61d8ccddaeec5f3fe4209da3a6168dbb91573e0 \
+    --hash=sha256:dc0b419a0cfeb6e8b34e85167c0da2671206f5095f1baa9663d23bcfd6b535fc
     # via -r main.in
 idna==3.10 \
     --hash=sha256:12f65c9b470abda6dc35cf8e63cc574b1c52b11df2c86030af0ac09b01b13ea9 \
@@ -357,9 +357,7 @@ pyyaml==6.0.2 \
 sniffio==1.3.1 \
     --hash=sha256:2f6da418d1f1e0fddd844478f41680e794e6051915791a034ff65e5f100525a2 \
     --hash=sha256:f4324edc670a0f49750a81b895f35c3adb843cca46f0530f79fc1babb23789dc
-    # via
-    #   anyio
-    #   httpx
+    # via anyio
 starlette==0.41.0 \
     --hash=sha256:39cbd8768b107d68bfe1ff1672b38a2c38b49777de46d2a592841d58e3bf7c2a \
     --hash=sha256:a0193a3c413ebc9c78bff1c3546a45bb8c8bcb4a84cae8747d650a65bd37210a