Incorrect Dynamo query in ` /api/v1/environments/{environment_api_key}/edge-identity-overrides`

Sentry Issue: [FLAGSMITH-API-5H1](https://flagsmith.sentry.io/issues/7225550511/?referrer=github_integration)

```
ClientError: An error occurred (ValidationException) when calling the Query operation: Invalid KeyConditionExpression: KeyConditionExpressions must only contain one condition per key
(12 additional frame(s) were not displayed)
...
File "edge_api/identities/views.py", line 403, in get_edge_identity_overrides
items = edge_identity_service.get_edge_identity_overrides(
File "edge_api/identities/edge_identity_service.py", line 15, in get_edge_identity_overrides
ddb_environment_v2_wrapper.get_identity_overrides_by_environment_id(
File "environments/dynamodb/wrappers/environment_wrapper.py", line 81, in get_identity_overrides_by_environment_id
return list(
File "environments/dynamodb/wrappers/base.py", line 64, in _iter_all_items
query_response = response_getter() # type: ignore[call-arg]
```

Start in environments/dynamodb/wrappers/environment_wrapper.py at get_identity_overrides_by_environment_id, then trace its use from edge_api/identities/edge_identity_service.py and edge_api/identities/views.py. Inspect the DynamoDB query conditions and reproduce the endpoint request. Done means the endpoint no longer raises the KeyConditionExpression ValidationException.

Written by the indexing model from the issue text.