Data defined assistant dialogs do not use the right title case for their name

[qgib]

Author Name: Harrissou Santanna (@DelazJ)
Original Redmine Issue: 19095
Affected QGIS version: 3.1(master)
Redmine category:gui

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When you click on the "Assistant..." entry of a data defined override widget, the dialog that opens will be of 'Symbol stroke color' type instead of 'Symbol Stroke Color' according to HIG.

[stev-0]

I presume this is because a lot of the parent dialogs only the first word is capitalised - e.g. Fill color, Stroke color, Stroke style. Not sure it's worth changing these just on this minor point.

[Pedro-Murteira]

Still valid on QGIS 3.22.3.

[alexbruy]

Valid with the latest QGIS 3.33 (2ae70eb)