Left-align a weirdly centered checkbox label

Using the property that GTK+ hasn’t deprecated yet.

(Why center a checkbox’s label anyway? It’s crazy
that I need to add an explicit property for this.
Y u no have decent defaults, GTK+?!)

Change-Id: I5d0c8a4f2133a43af80907d66b56cb6429a30cae

sc/uiconfig/scalc/ui/checkwarningdialog.ui

 <?xml version="1.0" encoding="UTF-8"?>
-<!-- Generated with glade 3.20.2 -->
+<!-- Generated with glade 3.22.0 -->
 <interface domain="sc">
   <requires lib="gtk+" version="3.18"/>
   <object class="GtkMessageDialog" id="CheckWarningDialog">
@@ -77,7 +77,7 @@
             <property name="visible">True</property>
             <property name="can_focus">True</property>
             <property name="receives_default">False</property>
-            <property name="xalign">0</property>
+            <property name="halign">start</property>
             <property name="active">True</property>
             <property name="draw_indicator">True</property>
           </object>

sc/uiconfig/scalc/ui/sharedwarningdialog.ui

 <?xml version="1.0" encoding="UTF-8"?>
-<!-- Generated with glade 3.20.2 -->
+<!-- Generated with glade 3.22.0 -->
 <interface domain="sc">
   <requires lib="gtk+" version="3.18"/>
   <object class="GtkMessageDialog" id="SharedWarningDialog">
+    <property name="can_focus">False</property>
     <property name="resizable">False</property>
     <property name="modal">True</property>
-    <property name="can_focus">False</property>
     <property name="type_hint">dialog</property>
     <property name="message_type">warning</property>
     <property name="buttons">ok</property>
@@ -33,6 +33,7 @@
             <property name="visible">True</property>
             <property name="can_focus">True</property>
             <property name="receives_default">False</property>
+            <property name="halign">start</property>
             <property name="draw_indicator">True</property>
           </object>
           <packing>