fix(executor_manager): add httpx dependency for validation status reporting

Add httpx>=0.24.0 to requirements.txt to fix CI test failure.
The httpx library is required by docker executor to report
validation stage progress to the backend API.

Author: qdaxb

executor_manager/requirements.txt

@@ -498,6 +498,8 @@ uvicorn==0.38.0 \
     --hash=sha256:48c0afd214ceb59340075b4a052ea1ee91c16fbc2a9b1469cca0e54566977b02 \
     --hash=sha256:fd97093bdd120a2609fc0d3afe931d4d4ad688b6e75f0f929fde1bc36fe0e91d
     # via executor-manager
+httpx>=0.24.0
+    # via executor-manager (for validation status reporting)
 websocket-client==1.9.0 \
     --hash=sha256:9e813624b6eb619999a97dc7958469217c3176312b3a16a4bd1bc7e08a46ec98 \
     --hash=sha256:af248a825037ef591efbf6ed20cc5faa03d3b47b9e5a2230a529eeee1c1fc3ef