## 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 posthog.models import Plugin, PluginSourceFile
    plugin_configs = (
        Plugin.objects.filter(pluginconfig__team_id=team_id, pluginconfig__enabled=True)
        .filter(
            pluginsourcefile__status=PluginSourceFile.Status.TRANSPILED,
            pluginsourcefile__filename="frontend.tsx",
        )
        .values(
            "pluginconfig__id",
            "pluginconfig__config",
            "config_schema",
            "id",
            "plugin_type",
            "name",
        )
        .all()
    )
    frontend_apps = {}
    for p in plugin_configs:
        config = p["pluginconfig__config"] or {}
        config_schema = p["config_schema"] or {}
        secret_fields = {field["key"] for field in config_schema if "secret" in field and field["secret"]}
        for key in secret_fields:
            if key in config:
                config[key] = "** SECRET FIELD **"
        frontend_apps[p["pluginconfig__id"]] = {
            "pluginConfigId": p["pluginconfig__id"],