Fix: Update clef elements when changing default instrument

[CubikingChill]

This fixes a regression introduced by 99b5b5b ("EditStaff: don't unexpectedly change clef when pressing OK without making changes").

That commit changed applyStaffProperties() to read the clef from m_staff->defaultClefType() instead of m_instrument.clefType(). However, showReplaceInstrumentDialog() never updates m_staff's default clef type when the instrument changes, so on the second apply() call (Apply then OK), applyStaffProperties() sends the stale old clef, reverting the change.

The fix adds m_staff->setDefaultClefType(m_instrument.clefType(0)) in showReplaceInstrumentDialog() to keep m_staff consistent with the selected instrument.

Resolves: #32633

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[CubikingChill]

Am I correct in understanding that this PR directly depends on #32499, which has not been merged yet?

Yes. But is sticking to the old way of setting part default clef better?

[CubikingChill]

Changed to a more minimal fix. Ready for review.

[mathesoncalum]

Looks good @CubikingChill. FYI I've re-committed with a more descriptive commit message (the original was just "fix"). If you could keep this in mind for any future PRs that would great - thank you!

[CubikingChill]

Noted. Thank you.

[CubikingChill]

Can you check the latest nightly? I don't think the fix works :（