FieldHelpButton: always show tooltip on click

Rather than toggling display of the tooltip.
Since the tooltip will show up on hover too, the user might quickly
hover then click on the button only to see the tooltip immediatly
disappear.

Closing the tooltip can still be done by moving the cursor away from the
button, or tapping on it/anywhere else.

src/gui/Base/Buttons/FieldHelpButton.qml

@@ -12,7 +12,7 @@ HButton {
     iconItem.small: true
     toolTip.text: helpText
 
-    onClicked: toolTip.instantToggle()
+    onClicked: toolTip.instantShow()
     onActiveFocusChanged: if (! activeFocus && toolTip.visible) toolTip.hide()
 
     Layout.fillHeight: true