chore(v3)!: remove unnecessary underscores

The arguments to `__exit__` are not used. When first implemented, this
used the leading underscores to make that explicit; however, this is
incompatible with the expected type signature of the function.

BREAKING CHANGE: The PactServer `__exit__` arguments no longer have
    leading underscores. This is typically handled by Python itself and
    therefore is unlikely to be a change for any user, unless the end
    user was calling the `__exit__` method explicitly _and_ using
    keyword arguments.

Signed-off-by: JP-Ellis <josh@jpellis.me>

src/pact/v3/pact.py

@@ -744,9 +744,9 @@ def __enter__(self) -> Self:
 
     def __exit__(
         self,
-        _exc_type: type[BaseException] | None,
-        _exc_value: BaseException | None,
-        _traceback: TracebackType | None,
+        exc_type: type[BaseException] | None,
+        exc_value: BaseException | None,
+        traceback: TracebackType | None,
     ) -> None:
         """
         Stop the server.