## Bug description

<img width="696" alt="Screen Shot 2021-09-16 at 2 37 41 PM" src="https://user-images.githubusercontent.com/13460330/133689529-c4fffc7f-53f8-494e-b7a8-7fb656fd50e6.png">

## Expected behavior

Bars and labels always show on top of axes and gridlines.

## How to reproduce

1. https://app.posthog.com/insights?insight=FUNNELS&properties=%5B%5D&filter_test_accounts=false&events=%5B%7B%22id%22%3A%22%24pageview%22%2C%22name%22%3A%22%24pageview%22%2C%22type%22%3A%22events%22%2C%22order%22%3A0%7D%2C%7B%22id%22%3A%22%24pageview%22%2C%22name%22%3A%22%24pageview%22%2C%22type%22%3A%22events%22%2C%22order%22%3A1%7D%2C%7B%22id%22%3A%22%24pageview%22%2C%22name%22%3A%22%24pageview%22%2C%22type%22%3A%22events%22%2C%22order%22%3A2%7D%5D&actions=%5B%5D&exclusions=%5B%5D&interval=day&funnel_from_step=0&funnel_to_step=1&new_entity=%5B%5D&funnel_viz_type=time_to_convert&display=FunnelViz

## Environment

- [X] PostHog Cloud
- [X] self-hosted PostHog (ClickHouse-based), version/commit: _please provide_
- [X] self-hosted PostHog (Postgres-based, legacy), version/commit: _please provide_

## Additional context



#### *Thank you* for your bug report – we love squashing them!

ee/clickhouse/queries/funnels/funnel_time_to_convert.py
]
        steps_average_conversion_time_expression_sum = " + ".join(steps_average_conversion_time_identifiers)
        steps_average_conditional_for_invalid_values = [
            f"{identifier} >= 0" for identifier in steps_average_conversion_time_identifiers
        ]
        
        
        
        query = f"""
            WITH
                step_runs AS (
                    SELECT * FROM (
                        {steps_per_person_query}
                    ) WHERE {" AND ".join(steps_average_conditional_for_invalid_values)}
                ),
                histogram_params AS (
                    /* Binning ensures that each sample belongs to a bin in results */
                    /* If bin_count is not a custom number, it's calculated in bin_count_expression */
                    SELECT
                        floor(min({steps_average_conversion_time_expression_sum})) AS from_seconds,
                        ceil(max({steps_average_conversion_time_expression_sum})) AS to_seconds,
                        round(avg({steps_average_conversion_time_expression_sum}), 2) AS average_conversion_time,
                        {bin_count_expression or ""}
                        ceil((to_seconds - from_seconds) / {bin_count_identifier}) AS bin_width_seconds_raw,
                        /* Use 60 seconds as fallback bin width in case of only one sample */
                        if(bin_width_seconds_raw > 0, bin_width_seconds_raw, 60) AS bin_width_seconds
                    FROM step_runs
                ),
                /* Below CTEs make histogram_params columns available to the query below as straightforward identifiers */
                ( SELECT bin_width_seconds FROM histogram_params ) AS bin_width_seconds,