Web Inspector: avoid recomputing duplicate properties when updating/moving a section

https://bugs.webkit.org/show_bug.cgi?id=318564

Reviewed by Timothy Hatcher.

* Source/WebInspectorUI/UserInterface/Views/SpreadsheetCSSStyleDeclarationEditor.js:
(WI.SpreadsheetCSSStyleDeclarationEditor.prototype._updatePropertiesStatus):
* Source/WebInspectorUI/UserInterface/Views/SpreadsheetStyleProperty.js:
(WI.SpreadsheetStyleProperty.calculateDuplicateProperties): Added.
(WI.SpreadsheetStyleProperty.prototype.updateStatus):

Canonical link: https://commits.webkit.org/322741@main