sambacc: do not require coverage for protocol types

Just something I noticed while I was looking over coverage for the
new types.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

sambacc/simple_waiter.py

@@ -66,11 +66,11 @@ class Waiter(typing.Protocol):
     """Waiter protocol - interfaces common to all waiters."""
 
     def wait(self) -> None:
-        ...
+        ...  # pragma: no cover
 
     def acted(self) -> None:
         """Inform that waiter that changes were made."""
-        ...
+        ...  # pragma: no cover
 
 
 def watch(