Revert "Turn semicolon as empty statement into an error"

[WalterBright]

Reverts #15072

Because it isn't really necessary to make empty statements an error, and it causes users unnecessary grief.

[dlang-bot]

Thanks for your pull request, @WalterBright!

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Testing this PR locally

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[dkorpel]

Because it isn't really necessary to make empty statements an error

Then why turn it back into a deprecation?

[WalterBright]

Because it's easier to review if it is only a revert. The deprecation can be removed as a follow-on.

[maxhaton]

Target stable

[WalterBright]

@maxhaton good idea! But I never remember how to do it - can you?

[ghost]

The situation is pretty simple right now. Either it was a deprecation so this PR has to be closed or the previous deprecation is turned into a warning.