feat: GtkSpinner => AdwSpinner (#211)

Author: GeopJr

data/ui/application.ui

@@ -325,12 +325,11 @@
 																											<object class="GtkStackPage">
 																												<property name="name">spinner</property>
 																												<property name="child">
-																													<object class="GtkSpinner">
+																													<object class="AdwSpinner">
 																														<property name="valign">center</property>
 																														<property name="halign">center</property>
 																														<property name="hexpand">1</property>
 																														<property name="vexpand">1</property>
-																														<property name="spinning">1</property>
 																														<property name="width-request">32</property>
 																														<property name="height-request">32</property>
 																													</object>