Bug 1559984 - Follow-up: Increase spinner duration to 6s to minimise visual artefacts. r=me DONTBUILD

--HG--
extra : amend_source : f059d43d68fce16f54146de3869a09013f6d8587

mail/themes/shared/mail/icons/search-spinner.svg

@@ -4,6 +4,6 @@
 
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 120" width="100px" height="120px">
   <circle fill="none" stroke="context-fill" stroke-opacity="context-fill-opacity" stroke-width="10" stroke-dasharray="36" cx="50" cy="70" r="45">
-    <animateTransform attributeName="transform" type="rotate" from="0 50 70" to="360 50 70" dur="2s" repeatCount="indefinite"/>
+    <animateTransform attributeName="transform" type="rotate" from="0 50 70" to="360 50 70" dur="6s" repeatCount="indefinite"/>
   </circle>
 </svg>