Consistent sizing between Combo and TextField

Also correctly set implicitHeight on QGCTextField

src/QmlControls/QGCComboBox.qml

@@ -19,7 +19,7 @@ ComboBox {
 
         background: Item {
             implicitWidth:      Math.round(ScreenTools.defaultFontPixelWidth * 4.5)
-            implicitHeight:     ScreenTools.isMobile ? Math.max(25, Math.round(ScreenTools.defaultFontPixelHeight * 2)) : Math.max(25, Math.round(ScreenTools.defaultFontPixelHeight * 1.2))
+            implicitHeight:     Math.round(ScreenTools.defaultFontPixelHeight * (ScreenTools.isMobile ? 2 : 1.2))
 
             Rectangle {
                 anchors.fill:   parent

src/QmlControls/QGCTextField.qml

@@ -26,7 +26,8 @@ TextField {
     QGCPalette { id: qgcPal; colorGroupEnabled: enabled }
 
     textColor:          qgcPal.textFieldText
-    height:             Math.round(Math.max(25, ScreenTools.defaultFontPixelHeight * (ScreenTools.isMobile ? 2.5 : 1.2)))
+
+    implicitHeight: Math.round(ScreenTools.defaultFontPixelHeight * (ScreenTools.isMobile ? 2 : 1.2))
 
     QGCLabel {
         id:             unitsLabelWidthGenerator