## 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
filter_dict = {
            "insight": "TRENDS",
            "properties": self.query.properties,
            "filter_test_accounts": self.query.filterTestAccounts,
            "date_to": self.query_date_range.date_to(),
            "date_from": self.query_date_range.date_from(),
            "entity_type": "events",
            "sampling_factor": self.query.samplingFactor,
            "aggregation_group_type_index": self.query.aggregation_group_type_index,
            "interval": self.query.interval,
        }
        if self.query.trendsFilter is not None:
            filter_dict.update(self.query.trendsFilter.__dict__)
        if self.query.breakdownFilter is not None:
            filter_dict.update(**self.query.breakdownFilter.__dict__)
        return {k: v for k, v in filter_dict.items() if v is not None}
    @cached_property
    def _trends_display(self) -> TrendsDisplay:
        if self.query.trendsFilter is None or self.query.trendsFilter.display is None:
            display = ChartDisplayType.ActionsLineGraph
        else:
            display = self.query.trendsFilter.display
        return TrendsDisplay(display)