Keep the docs watch-loop snippet ASCII

The docs-example checker pipes snippets to ruff in the platform
encoding; an em-dash in a code comment arrives as invalid UTF-8 on
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Author: maxisbey

docs/handlers/subscriptions.md

@@ -107,7 +107,7 @@ async def watch(client: Client, uri: str) -> None:
                 async for _event in sub:
                     await client.read_resource(uri)
         except SubscriptionLost:
-            continue  # transport dropped — re-listen
+            continue  # transport dropped - re-listen
         else:
             break  # the server ended it deliberately
 ```