## Bug description

The grouped-by-month view in charts is hella confusing. The x-axis shows a date that does not reflect the value on the y-axis.

1. the y-axis shows the number for the END of the month
2. the x-axis reads as "beginning of the month"

![CleanShot 2024-02-05 at 10 23 30@2x](https://github.com/PostHog/posthog/assets/35429197/d78df745-8319-4b78-95fa-d96f18aee357)

### Comparison with daily grouping

Compare the "group by month" view with "group by day". The x-axis labeling aligns with the y-axis values. 

![CleanShot 2024-02-05 at 10 29 20@2x](https://github.com/PostHog/posthog/assets/35429197/998825fa-7406-4214-8310-8f173980f80c)


## How to reproduce

1. Group a chart by month 
2. select "unique events"

## Proposal 

### 1. easy fix - remove the "1." from the labelling

- will still confuse readers with "is this the beginning or end of the month"

![CleanShot 2024-02-05 at 10 23 30@2x](https://github.com/PostHog/posthog/assets/35429197/1a0ae6d4-0e02-4b32-86ab-7b0e069655ed)

### 2. correct fix - show end of month

- removes ambiguity from "is that the beginning or end of month"
- harder to implement because months have different end days

![CleanShot 2024-02-05 at 10 23 30@2x](https://github.com/PostHog/posthog/assets/35429197/61226346-7f97-4bcd-87bf-53fc83c75245)


cc @jannesblobel
posthog/utils.py
context["js_posthog_api_key"] = f"'{api_token}'"
            context["js_posthog_host"] = "window.location.origin"
    else:
        context["js_posthog_api_key"] = "'sTMFPsFhdP1Ssg'"
        context["js_posthog_host"] = "'https://app.posthog.com'"
    context["js_capture_time_to_see_data"] = settings.CAPTURE_TIME_TO_SEE_DATA
    context["js_kea_verbose_logging"] = settings.KEA_VERBOSE_LOGGING
    context["js_url"] = get_js_url(request)
    try:
        year_in_hog_url = f"/year_in_posthog/2023/{str(request.user.uuid)}"  
    except:
        year_in_hog_url = None
    posthog_app_context: Dict[str, Any] = {
        "persisted_feature_flags": settings.PERSISTED_FEATURE_FLAGS,
        "anonymous": not request.user or not request.user.is_authenticated,
        "year_in_hog_url": year_in_hog_url,
    }
    posthog_bootstrap: Dict[str, Any] = {}
    posthog_distinct_id: Optional[str] = None
    
    if not request.GET.get("no-preloaded-app-context"):
        from posthog.api.shared import TeamPublicSerializer
        from posthog.api.team import TeamSerializer
        from posthog.api.user import UserSerializer
        from posthog.user_permissions import UserPermissions
        from posthog.views import preflight_check
        posthog_app_context = {
            "current_user": None,
            "current_team": None,
            "preflight": json.loads(preflight_check(request).getvalue()),