Bug 1583951 - Remove XUL grid from printPreviewProgress.xul. r=mconley

Differential Revision: https://phabricator.services.mozilla.com/D53307

--HG--
extra : moz-landing-system : lando

toolkit/components/printing/content/printPreviewProgress.xul

@@ -21,25 +21,13 @@
 
   <script src="chrome://global/content/printPreviewProgress.js"/>
 
-    <grid flex="1">
-      <columns>
-        <column/>
-        <column/>
-      </columns>
+  <box flex="1" style="display: grid; grid-template-columns: min-content max-content; grid-template-rows: max-content max-content;">
+    <!-- First row -->
+    <label id="dialog.titleLabel" data-l10n-id="print-title" style="justify-self: end;"/>
+    <label id="dialog.title"/>
 
-      <rows>
-        <row>
-          <hbox pack="end">
-            <label id="dialog.titleLabel" data-l10n-id="print-title"/>
-          </hbox>
-          <label id="dialog.title"/>
-        </row>
-        <row class="thin-separator">
-          <hbox pack="end">
-            <label id="dialog.progressSpaces" data-l10n-id="print-preparing"/>
-          </hbox>
-          <label id="dialog.progressLabel" data-l10n-id="print-progress"/>
-        </row>
-      </rows>
-    </grid>
+    <!-- Second row -->
+    <label id="dialog.progressSpaces" data-l10n-id="print-preparing" style="justify-self: end;"/>
+    <label id="dialog.progressLabel" data-l10n-id="print-progress"/>
+  </box>
 </dialog>