Prefer `type(x) is int` to `isinstance(x, int)` (#14945)

* Perfer `type(x) is int` to `isinstance(x, int)`

This covered all additional instances I could see where `x` was
user-controlled.
The remaining cases are

```
$ rg -s 'isinstance.*[^_]int'
tests/replication/_base.py
576:        if isinstance(obj, int):

synapse/util/caches/stream_change_cache.py
136:        assert isinstance(stream_pos, int)
214:        assert isinstance(stream_pos, int)
246:        assert isinstance(stream_pos, int)
267:        assert isinstance(stream_pos, int)

synapse/replication/tcp/external_cache.py
133:        if isinstance(result, int):

synapse/metrics/__init__.py
100:        if isinstance(calls, (int, float)):

synapse/handlers/appservice.py
262:        assert isinstance(new_token, int)

synapse/config/_util.py
62:        if isinstance(p, int):
```

which cover metrics, logic related to `jsonschema`, and replication and
data streams. AFAICS these are all internal to Synapse

* Changelog

1 files changed, 1 insertions, 1 deletions

diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 3278a695ed..6290f7f523 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -377,7 +377,7 @@ class MessageHandler:
         """
 
         expiry_ts = event.content.get(EventContentFields.SELF_DESTRUCT_AFTER)
-        if not isinstance(expiry_ts, int) or event.is_state():
+        if type(expiry_ts) is not int or event.is_state():
             return
 
         # _schedule_expiry_for_event won't actually schedule anything if there's already