Add "MB" suffix to the "edit partition" size box.

Makes it easier to know which unit Calamares is using when
resizing a partition. The "Create partition" dialog has
it already.

src/modules/partition/gui/EditExistingPartitionDialog.ui

@@ -124,7 +124,11 @@
       </widget>
      </item>
      <item row="1" column="1">
-      <widget class="QSpinBox" name="sizeSpinBox"/>
+      <widget class="QSpinBox" name="sizeSpinBox">
+       <property name="suffix">
+        <string> MB</string>
+       </property>
+      </widget>
      </item>
      <item row="5" column="0">
       <widget class="QLabel" name="fileSystemLabel">