chore(docs): fix minor small typos (#5124)

api/core/model_runtime/docs/en_US/interfaces.md

@@ -336,7 +336,7 @@ Inherit the `__base.text2speech_model.Text2SpeechModel` base class and implement
 - Invoke Invocation
 
   ```python
-  def _invoke(elf, model: str, credentials: dict, content_text: str, streaming: bool, user: Optional[str] = None):
+  def _invoke(self, model: str, credentials: dict, content_text: str, streaming: bool, user: Optional[str] = None):
       """
       Invoke large language model
   

api/core/model_runtime/docs/zh_Hans/interfaces.md

@@ -376,7 +376,7 @@ class XinferenceProvider(Provider):
 - Invoke 调用
 
   ```python
-  def _invoke(elf, model: str, credentials: dict, content_text: str, streaming: bool, user: Optional[str] = None):
+  def _invoke(self, model: str, credentials: dict, content_text: str, streaming: bool, user: Optional[str] = None):
       """
       Invoke large language model