## 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
if request.method == "POST":
        if request.content_type in ["", "text/plain", "application/json"]:
            data = request.body
        else:
            data = request.POST.get("data")
    else:
        data = request.GET.get("data")
        if data:
            KLUDGES_COUNTER.labels(kludge="data_in_get_param").inc()
    
    with configure_scope() as scope:
        if isinstance(data, dict):
            scope.set_context("data", data)
        scope.set_tag(
            "origin",
            request.headers.get("origin", request.headers.get("remote_host", "unknown")),
        )
        scope.set_tag("referer", request.headers.get("referer", "unknown"))
        
        scope.set_tag("library.version", request.GET.get("ver", "unknown"))
    compression = (
        request.GET.get("compression") or request.POST.get("compression") or request.headers.get("content-encoding", "")
    ).lower()
    return decompress(data, compression)
class SingletonDecorator: