kcm/screenedges: Fix default indicator for corner ratio

When setting the default value for `ElectricCornerRatio` in the UI form
we also need to update the default indicator for this field.

*Default value for this setting is 25%*
| BEFORE | AFTER |
|---|---|
|![screenedges_25_before](/uploads/2e9f21627cc05cd12fd45ec1a019b89e/screenedges_25_before.png)|![screenedges_25_after](/uploads/7106341983e4cce0a4fb26000fb8583f/screenedges_25_after.png)|

BUG: 448886
FIXED-IN: 5.24

src/kcmkwin/kwinscreenedges/kwinscreenedgeconfigform.cpp

@@ -45,6 +45,7 @@ void KWinScreenEdgesConfigForm::setElectricBorderCornerRatio(double value)
 void KWinScreenEdgesConfigForm::setDefaultElectricBorderCornerRatio(double value)
 {
     m_defaultCornerRatio = value;
+    updateDefaultIndicators();
 }
 
 double KWinScreenEdgesConfigForm::electricBorderCornerRatio() const