## 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
trends_query=self.query,
                team=self.team,
                query_date_range=query_date_range,
                series=series,
                timings=self.timings,
                modifiers=self.modifiers,
            )
            breakdown = query_builder._breakdown(is_actors_query=False)
            if not breakdown.enabled:
                break
            is_boolean_breakdown = self._is_breakdown_field_boolean()
            is_histogram_breakdown = breakdown.is_histogram_breakdown
            breakdown_values: List[str | int]
            res_breakdown = []
            if is_histogram_breakdown:
                buckets = breakdown._get_breakdown_histogram_buckets()
                breakdown_values = [f"[{t[0]},{t[1]}]" for t in buckets]
                breakdown_values.append('["",""]')
            else:
                breakdown_values = breakdown._get_breakdown_values
            for value in breakdown_values:
                if self.query.breakdownFilter is not None and self.query.breakdownFilter.breakdown_type == "cohort":
                    cohort_name = "all users" if str(value) == "0" else Cohort.objects.get(pk=value).name
                    label = cohort_name
                    value = value
                elif value == BREAKDOWN_OTHER_STRING_LABEL or value == BREAKDOWN_OTHER_NUMERIC_LABEL:
                    
                    
                    continue  
                elif value == BREAKDOWN_NULL_STRING_LABEL or value == BREAKDOWN_NULL_NUMERIC_LABEL: