Document Sketcher edit value menu label

[kaycke1337]

Refs #94.

Summary:

• Update the Sketcher constraints context-menu label from "Change Value" to "Edit Value".
• Keep the Sketcher Dialog and Workbench pages aligned with the FreeCAD 1.2 UI text.

Source:

• Sketcher: change 'Change Value' to 'Edit Value' in task panel FreeCAD/FreeCAD#29556

Validation:

• git diff --check -- wiki/Sketcher_Dialog.wikitext wiki/Sketcher_Workbench.wikitext