[6.x] Fix expanding Bard sets in localized entries

[duncanmcclean]

This pull request fixes an issue where clicking on a Bard set header wouldn't expand/collapse the set when viewing a localized entry with collapse: true and localizable: true configured on the field.

This was happening because Set.vue was reading the collapsed state from bard.meta.collapsed (the prop) instead of bard.collapsed (the reactive data property that gets modified by the expand/collapse methods).

This PR fixes it by reading from the collapsed data property instead.

Fixes #14131

[AtmoFX]

@duncanmcclean I'm encountering considerable issues expanding sets in Bard after upgrading.

Symptoms are:

• Sets do not expand when clicking on the set bar (sometimes they do but they often don't).
• Sets do not expand when clicking on the menu > Expand set
• Menu shows Collapse set when a set is not expanded (though I believe it shows Collapse set only after clicking on the set bar).

Based on last point, I believe the expanded/collapsed status is correctly changed but the browser (Firefox) fails to reflect it.

I did not manage to revert the issue by editing this PR's files back to the previous text but this PR remains my best guess as to what happened to my experience since last upgrade + I must say I was surprised by

The parameter used to be named value, is now named collapsed but the function's body still references value.

[duncanmcclean]

@AtmoFX Fixed in #14238.