## 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
from django.utils import timezone
from rest_framework.request import Request
from sentry_sdk import configure_scope
from sentry_sdk.api import capture_exception
from posthog.cloud_utils import get_cached_instance_license, is_cloud
from posthog.constants import AvailableFeature
from posthog.exceptions import RequestParsingError
from posthog.git import get_git_branch, get_git_commit
from posthog.metrics import KLUDGES_COUNTER
from posthog.redis import get_client
if TYPE_CHECKING:
    from django.contrib.auth.models import AbstractBaseUser, AnonymousUser
    from posthog.models import Team, User
DATERANGE_MAP = {
    "minute": datetime.timedelta(minutes=1),
    "hour": datetime.timedelta(hours=1),
    "day": datetime.timedelta(days=1),
    "week": datetime.timedelta(weeks=1),
    "month": datetime.timedelta(days=31),
}
ANONYMOUS_REGEX = r"^([a-z0-9]+\-){4}([a-z0-9]+)$"
DEFAULT_DATE_FROM_DAYS = 7
logger = structlog.get_logger(__name__)
__location__ = os.path.realpath(os.path.join(os.getcwd(), os.path.dirname(__file__)))
def format_label_date(date: datetime.datetime, interval: str) -> str:
    labels_format = "%-d-%b-%Y"
    if interval == "hour":
        labels_format += " %H:%M"
    return date.strftime(labels_format)
class PotentialSecurityProblemException(Exception):