Fix issue 19939 - std.format count width error

[shove70]

No description provided.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	19939	normal	std.format %13,3.2f does not count width correctly

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 + phobos#7068"

[quickfur]

LGTM. Thanks!

[shove70]

@n8sh @quickfur, Thanks.

[thewilsonator]

this should probably target stable.

[n8sh]

Changing to target stable.