fix: remove unused modified_count variable (F841)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Dhanushree-Microsoft

src/processor/src/libs/agent_framework/middlewares.py

@@ -146,7 +146,6 @@ async def process(
 
         # Modify user messages by creating new messages with enhanced text
         modified_messages: list[Message] = []
-        modified_count = 0
 
         for message in context.messages:
             if message.role == ROLE_USER and message.text:
@@ -161,7 +160,6 @@ async def process(
 
                 modified_message = Message(role=message.role, text=updated_text, contents=updated_text)
                 modified_messages.append(modified_message)
-                modified_count += 1
             else:
                 modified_messages.append(message)