[wdspec] bidi: remove unused fixture (#40949)

diff --git a/webdriver/tests/bidi/__init__.py b/webdriver/tests/bidi/__init__.py
index a6c3dbd..eb41273 100644
--- a/webdriver/tests/bidi/__init__.py
+++ b/webdriver/tests/bidi/__init__.py
@@ -67,10 +67,6 @@
     return _
 
 
-def positive_int(actual: Any) -> None:
-    assert isinstance(actual, int) and actual > 0
-
-
 async def create_console_api_message(bidi_session, context: str, text: str):
     await bidi_session.script.call_function(
         function_declaration="""(text) => console.log(text)""",