## Bug description

If I mark an insight as a favorite (⭐) and then refresh, the insight is no longer marked as a favorite although it is (can see it in Favorites).

<img width="390" alt="image" src="https://user-images.githubusercontent.com/30181361/182802236-9ecf0531-899c-4f25-ae86-bc233cefdc2f.png">

Note that I'm in the _Favorites_ tab and that _Bug example_ is not starred.
## Environment

- [x] PostHog Cloud
- [ ] self-hosted PostHog, version/commit: please provide

posthog/api/insight.py
result = serializers.SerializerMethodField()
    last_refresh = serializers.SerializerMethodField(
        read_only=True,
        help_text="""
    The datetime this insight's results were generated.
    If added to one or more dashboards the insight can be refreshed separately on each.
    Returns the appropriate last_refresh datetime for the context the insight is viewed in
    (see from_dashboard query parameter).
    """,
    )
    created_by = UserBasicSerializer(read_only=True)
    last_modified_by = UserBasicSerializer(read_only=True)
    effective_privilege_level = serializers.SerializerMethodField()
    timezone = serializers.SerializerMethodField(help_text="The timezone this chart is displayed in.")
    dashboards = serializers.PrimaryKeyRelatedField(
        help_text="A dashboard ID for each of the dashboards that this insight is displayed on.",
        many=True,
        required=False,
        queryset=Dashboard.objects.filter(deleted=False),
    )
    filters_hash = serializers.CharField(
        read_only=True,
        help_text="""A hash of the filters that generate this insight.
        Used as a cache key for this result.
        A different hash will be returned if loading the insight on a dashboard that has filters.""",
    )
    class Meta: