set Bitwarden-Client-Version header to not generate a warning on every request

avoid this warning in vaultwarden server logs:
> Unauthorized Error: No Bitwarden-Client-Version header provided

version number cribbed from bitwarden test suite. the value is not
checked, other than that it looks like a SemVer string.

Author: uedvt359

src/vaultwarden/clients/bitwarden.py

@@ -34,6 +34,9 @@ def __init__(
         self._http_client = Client(
             base_url=f"{self.url}/",
             event_hooks={"response": [log_raise_for_status]},
+            headers={
+                "Bitwarden-Client-Version": "2024.1.0"
+            },
             timeout=timeout,
         )
         self._connect_token: ConnectToken | None = None