chore: relax HTTPX version upper bound

Closes: #313

Author: vdusek

poetry.lock

@@ -41,9 +41,7 @@ keywords = [
 [tool.poetry.dependencies]
 python = "^3.9"
 apify-shared = ">=1.1.2"
-# TODO: relax the upper bound once the issue is resolved:
-# https://github.com/apify/apify-client-python/issues/313
-httpx = ">=0.25 <0.28.0"
+httpx = ">=0.25"
 more_itertools = ">=10.0.0"
 
 [tool.poetry.group.dev.dependencies]
@@ -60,7 +58,7 @@ pytest-only = "~2.1.0"
 pytest-timeout = "~2.3.0"
 pytest-xdist = "~3.6.0"
 redbaron = "~0.9.0"
-respx = "^0.21.1"
+respx = "~0.22.0"
 ruff = "~0.8.0"
 setuptools = "~75.6.0"     # setuptools are used by pytest but not explicitly required