Fix 24339 - std.mmfile has poor documentation

[dkorpel]

No description provided.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	24339	minor	std.mmfile has poor documentation

Testing this PR locally

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

dub run digger -- build "master + phobos#8891"

[cyrusmsk]

Thank you @dkorpel and @thewilsonator for that

[AndrejMitrovic]

Is this an incomplete sentence?

[dkorpel]

Good catch, #8892