Remove await from usage.incr() in tool manager

The incr() method is synchronous (uses threading.Lock), not async,
so we should not await it.

Author: certainly-param

pydantic_ai_slim/pydantic_ai/_tool_manager.py

@@ -234,7 +234,7 @@ async def _call_function_tool(
         ) as span:
             try:
                 tool_result = await self._call_tool(call, allow_partial, wrap_validation_errors)
-                await usage.incr(RunUsage(tool_calls=1))
+                usage.incr(RunUsage(tool_calls=1))
 
             except ToolRetryError as e:
                 part = e.tool_retry