Revert "Ensure new/updated rows having a changed_at greater than all previous ones"

[Al2Klimov]

This reverts commit 5ddc751.

As you requested, now completely different channels won't conflict (40001) w/ each other, as they don't SELECT a common MAX(changed_at) in a serializable tx.

But one and the same e.g channel would still conflict (40001) if updated by two users which is good.

[Al2Klimov]

@julianbrost @oxzi @nilmerg But, honestly speaking, as I already said:

Web is a point&click thing, so generally the users are slow enough not to run into #311 (40001 error), ex. once or twice a year.

It is simply the right thing that a row, which is committed later, has a greater changed_at than previous ones. Especially if our incremental config update mechanism relies on it!

[julianbrost]

I'm missing context to understand what you're doing here.

[Al2Klimov]

The point is, our incremental config update mechanism relies on strongly sequential changed_at not to miss any updates. I ensured this consistency with this:

• Ensure new/updated rows having a changed_at greater than all previous ones #311

And now @nilmerg says, like, Oh no! Now, whenever two user edit distinct channels during the same(!) very few ms [which happens.. once a year? twice.. ? Who cares?], one of them gets an error message [saying that tx serialization failed or similar] and has to re-submit. This is bad!