Combobox height/width was being resized by RowLayout causing it to be squished. Assigned a implicit width/height which is used instead of height/width.

CURA-8688

resources/qml/Dialogs/DiscardOrKeepProfileChangesDialog.qml

@@ -91,10 +91,12 @@ UM.Dialog
     buttonSpacing: UM.Theme.getSize("thin_margin").width
 
     leftButtons: [
-        ComboBox
+        Cura.ComboBox
         {
+            implicitHeight: UM.Theme.getSize("combobox_dialog").height
+            implicitWidth: UM.Theme.getSize("combobox_dialog").width
+
             id: discardOrKeepProfileChangesDropDownButton
-            width: 300
             textRole: "text"
 
             model: ListModel

resources/themes/cura-light/theme.json

@@ -620,6 +620,7 @@
         "checkbox_label_padding": [0.5, 0.5],
 
         "spinbox": [6.0, 3.0],
+        "combobox_dialog": [14, 2],
 
         "tooltip": [20.0, 10.0],
         "tooltip_margins": [1.0, 1.0],