fix: use `removeprefix()` instead of `lstrip()` to remove the `data:` prefix (#11272)

Signed-off-by: -LAN- <laipz8200@outlook.com>

api/core/model_runtime/model_providers/moonshot/llm/llm.py

                 # ignore sse comments
                 if chunk.startswith(":"):
                     continue
-                decoded_chunk = chunk.strip().lstrip("data: ").lstrip()
+                decoded_chunk = chunk.strip().removeprefix("data: ")
                 chunk_json = None
                 try:
                     chunk_json = json.loads(decoded_chunk)

api/core/model_runtime/model_providers/openai_api_compatible/llm/llm.py

                 # ignore sse comments
                 if chunk.startswith(":"):
                     continue
-                decoded_chunk = chunk.strip().lstrip("data: ").lstrip()
+                decoded_chunk = chunk.strip().removeprefix("data: ")
                 if decoded_chunk == "[DONE]":  # Some provider returns "data: [DONE]"
                     continue
 

api/core/model_runtime/model_providers/stepfun/llm/llm.py

                 # ignore sse comments
                 if chunk.startswith(":"):
                     continue
-                decoded_chunk = chunk.strip().lstrip("data: ").lstrip()
+                decoded_chunk = chunk.strip().removeprefix("data: ")
                 chunk_json = None
                 try:
                     chunk_json = json.loads(decoded_chunk)