## 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
"type": "person",
                    "uuid": str(person3.uuid),
                    "value_at_data_point": 1,  
                },
            ]
            people_value_2 = self._get_trend_people(
                Filter(team=self.team, data={**data, "breakdown_value": "value_2"}),
                entity,
            )
            assert people_value_2 == [
                {
                    "created_at": "2020-01-01T12:00:00Z",
                    "distinct_ids": ["person2"],
                    "id": str(person2.uuid),
                    "is_identified": False,
                    "matched_recordings": [],
                    "name": "person2",
                    "properties": {},
                    "type": "person",
                    "uuid": str(person2.uuid),
                    "value_at_data_point": 1,  
                }
            ]
    @also_test_with_materialized_columns(person_properties=["name"])
    def test_breakdown_by_person_property_pie(self):
        self._create_multiple_people()
        with freeze_time("2020-01-04T13:01:01Z"):
            event_response = self._run(
                Filter(
                    team=self.team,