fix issue 19584 - Illegal optimization: Shift-or -> imul

[ghost]

Regression was caused by #2333. The change is simply removed because the other compilers don't optimize either, see for example.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	19584	regression	Illegal optimization: Shift-or -> imul

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "stable + dmd#9990"

[thewilsonator]

cc @WalterBright

[ghost]

@thewilsonator there's nothing else to do there. Even LDC, the huge big backend and all the "brains" that have contributed to make it, does not optimize the operations that are involved.

[JinShil]

Better to not have the regression than to have the optimization.