Docker Image crashing on Start

I had some difficulties getting opencov to run. The Docker Image on dockerhub wouldn't start at all so i built it myself.

With `docker-compose run opencov mix phx.server` i got the following error:

```
10:35:37.186 [info] Running Opencov.Endpoint with Cowboy using http://0.0.0.0:4000
10:35:40.013 [info] tzdata release in place is from a file last modified Mon, 20 Mar 2017 18:53:44 GMT. Release file on server was last modified Tue, 29 Dec 2020 17:00:24 GMT.
10:35:41.210 [error] GenServer :tzdata_release_updater terminating
** (FunctionClauseError) no function clause matching in Tzdata.Util.first_matching_weekday_in_month/4
(tzdata) lib/tzdata/util.ex:73: Tzdata.Util.first_matching_weekday_in_month(1932, 4, 7, [])
(tzdata) lib/tzdata/util.ex:293: Tzdata.Util.time_for_rule/2
(tzdata) lib/tzdata/period_builder.ex:158: Tzdata.PeriodBuilder.calc_periods_for_year/9
(tzdata) lib/tzdata/period_builder.ex:177: Tzdata.PeriodBuilder.calc_periods_for_year/9
(tzdata) lib/tzdata/period_builder.ex:182: Tzdata.PeriodBuilder.calc_periods_for_year/9
(tzdata) lib/tzdata/period_builder.ex:177: Tzdata.PeriodBuilder.calc_periods_for_year/9
(tzdata) lib/tzdata/period_builder.ex:182: Tzdata.PeriodBuilder.calc_periods_for_year/9
(tzdata) lib/tzdata/period_builder.ex:177: Tzdata.PeriodBuilder.calc_periods_for_year/9
Last message: :check_if_time_to_update
```

With `tzdata, :autoupdate, :disabled` in the config file it works, but i am not really sure why. Maybe other People will run into this problem as well.

Reproduce the failure with `docker-compose run opencov mix phx.server` and inspect the Docker image startup path and the config entry containing `tzdata, :autoupdate, :disabled`. Use the reported Tzdata stack trace as the entry point; done means the Docker image starts without the updater crash while retaining the intended timezone-data behavior.

Written by the indexing model from the issue text.