[gnome-builder] plugins/grep: fix size of activity spinner

[Christian Hergert <chergert src gnome org>]

commit 35dcc5daa4c5db029fc1f4ce7e557759b5fa2f7a
Author: Christian Hergert <chergert redhat com>
Date:   Thu Jul 14 11:47:15 2022 -0700

    plugins/grep: fix size of activity spinner
    
    Fixes #1712

 src/plugins/grep/gbp-grep-panel.ui | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/plugins/grep/gbp-grep-panel.ui b/src/plugins/grep/gbp-grep-panel.ui
index e14d525cf..0642ebad3 100644
--- a/src/plugins/grep/gbp-grep-panel.ui
+++ b/src/plugins/grep/gbp-grep-panel.ui
@@ -27,6 +27,8 @@
             </child>
             <child>
               <object class="GtkSpinner" id="spinner">
+                <property name="halign">center</property>
+                <property name="valign">center</property>
                 <property name="visible">True</property>
               </object>
             </child>