[SOGo] Fix vacation auto reply date shifting

[FreddleSpl0it]

Contribution Guidelines

• I've read the contribution guidelines and wholeheartedly agree them

What does this PR include?

Short Description

This PR fixes #5394

Affected Containers

• SOGo

Did you run tests?

What did you tested?

At SOGo container startup, I checked that the timezone was written to /etc/timezone.

What were the final results? (Awaited, got)

At SOGo container startup, the timezone was successfully written to /etc/timezone.

[DerLinkman]

Did you tested the vacation filters inside sogo?

Does it work as expected?

[FreddleSpl0it]

I was able to replicate the issue on the master branch following the steps described in Issue #5394

1. Use mailcow with other timezone than UTC (e.g. Europe/Prague in my case)
2. Set vacation in SOGo with start and end dates (https://imgur.com/tNPmyd9)
3. Login to mailcow UI and click the "[Show active user sieve filter]" button (https://imgur.com/RmI2Jeb)
4. Observe that SOGo created a Sieve filter with correct dates
5. Wait 5 minutes so the Ofelia "sogo_eautoreply" job is run
6. Click the "[Show active user sieve filter]" button again (https://imgur.com/zt0BpZ6)
7. Observe that both the start and end date are shifted one day backwards so they do not correspond to dates that are set in SOGo

With the applied fix, there was no shift in the dates.