## 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/utils.py
start_date = (start_date.replace(day=1)).replace(day=1)
        while start_date <= end_date:
            time_range.append(start_date)
            start_date = (start_date.replace(day=1) + delta).replace(day=1)
    return time_range
def get_safe_cache(cache_key: str):
    try:
        cached_result = cache.get(cache_key)  
        return cached_result
    except Exception:  
        try:
            cache.delete(cache_key)  
        except Exception:
            pass
    return None
def is_anonymous_id(distinct_id: str) -> bool:
    
    return bool(re.match(ANONYMOUS_REGEX, distinct_id))
def is_valid_regex(value: Any) -> bool:
    try:
        re.compile(value)
        return True
    except re.error:
        return False
def get_absolute_path(to: str) -> str:
    """
    Returns an absolute path in the FS based on posthog/posthog (back-end root folder)
    """
    return os.path.join(__location__, to)
class GenericEmails: