## 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/test/test_trends.py
self._create_person(team_id=self.team.pk, distinct_ids=["person_1"], properties={"name": "John"})
        self._create_person(team_id=self.team.pk, distinct_ids=["person_2"], properties={"name": "Jane"})
        self._create_event(
            event="event_name",
            team=self.team,
            distinct_id="person_1",
            properties={"$browser": "Safari"},
        )
        self._create_event(
            event="event_name",
            team=self.team,
            distinct_id="person_2",
            properties={"$browser": "Chrome"},
        )
        self._create_event(
            event="event_name",
            team=self.team,
            distinct_id="person_2",
            properties={"$browser": "Safari"},
        )
        cohort = _create_cohort(
            team=self.team,
            name="cohort1",
            groups=[{"properties": [{"key": "name", "value": "Jane", "type": "person"}]}],
        )
        response = self._run(
            Filter(
                team=self.team,
                data={