Remove the type hitn overloads.

In other repos, there's code like this:

Unfortunately, pyright cannot tell that the protocol argument is always 'tcp' in this case, only that the protocol is one of tcp/udp/icmp, and that's too broad to fit the righter overloaded specs, so it complains. This could be handled with changes in the upstream places, but I don't see any simple way to handle it within ops itself.

This was a minor improvement and not really needed, plus it's in the two methods that we're wanting to move people away from, so drop this change.

ops/model.py

@@ -593,15 +593,6 @@ def add_secret(self, content: Dict[str, str], *,
             owner='unit')
         return Secret(self._backend, id=id, label=label, content=content)
 
-    if typing.TYPE_CHECKING:
-        @typing.overload
-        def open_port(self, protocol: typing.Literal['tcp', 'udp'], port: int) -> None:  # noqa
-            ...
-
-        @typing.overload
-        def open_port(self, protocol: typing.Literal['icmp'], port: None = None) -> None:  # noqa
-            ...
-
     def open_port(self, protocol: typing.Literal['tcp', 'udp', 'icmp'],
                   port: Optional[int] = None) -> None:
         """Open a port with the given protocol for this unit.
@@ -637,15 +628,6 @@ def open_port(self, protocol: typing.Literal['tcp', 'udp', 'icmp'],
             raise ModelError(f"{normalised_protocol} must have a port number specified")
         self._backend.open_port(normalised_protocol, port)
 
-    if typing.TYPE_CHECKING:
-        @typing.overload
-        def close_port(self, protocol: typing.Literal['tcp', 'udp'], port: int) -> None:  # noqa
-            ...
-
-        @typing.overload
-        def close_port(self, protocol: typing.Literal['icmp'], port: None = None) -> None:  # noqa
-            ...
-
     def close_port(self, protocol: typing.Literal['tcp', 'udp', 'icmp'],
                    port: Optional[int] = None) -> None:
         """Close a port with the given protocol for this unit.