Give action button a sane default height

We don't want to give it a default width since that should just adjust to its contents by default, which is fine.

Contributes to issue CURA-5876.

resources/qml/ActionPanel/OutputProcessWidget.qml

@@ -104,7 +104,6 @@ Column
         {
             id: previewStageShortcut
 
-            height: UM.Theme.getSize("action_button").height
             text: catalog.i18nc("@button", "Preview")
             color: UM.Theme.getColor("secondary")
             hoverColor: UM.Theme.getColor("secondary")

resources/qml/ActionPanel/SliceProcessWidget.qml

@@ -85,7 +85,6 @@ Column
     {
         id: prepareButton
         width: parent.width
-        height: UM.Theme.getSize("action_button").height
         fixedWidthMode: true
         text:
         {