## 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/hogql_queries/insights/trends/trends_query_runner.py
else:
                    count = float(sum(get_value("total", val)))
                series_object = {
                    "data": get_value("total", val),
                    "labels": [
                        item.strftime(
                            "%-d-%b-%Y{}".format(" %H:%M" if self.query_date_range.interval_name == "hour" else "")
                        )
                        for item in get_value("date", val)
                    ],
                    "days": [
                        item.strftime(
                            "%Y-%m-%d{}".format(" %H:%M:%S" if self.query_date_range.interval_name == "hour" else "")
                        )
                        for item in get_value("date", val)
                    ],
                    "count": count,
                    "label": "All events" if series_label is None else series_label,
                    "filter": self._query_to_filter(),
                    "action": {  
                        "days": self.query_date_range.all_values(),
                        "id": series_label,
                        "type": "events",
                        "order": series.series_order,
                        "name": series_label or "All events",
                        "custom_name": None,
                        "math": series.series.math,
                        "math_property": None,
                        "math_hogql": None,
                        "math_group_type_index": None,