[JENKINS-75615] remove jenkins-avatar class

the jenkins-avatar class should only be applied on the UserAction and
not on every icon.

Author: mawinter69

core/src/main/resources/lib/layout/header/actions.jelly

@@ -46,7 +46,7 @@
         <x:attribute name="data-type">header-action</x:attribute>
         <x:attribute name="draggable">false</x:attribute>
         <x:attribute name="class">jenkins-button ${isCurrent ? '' : 'jenkins-button--tertiary'}</x:attribute>
-        <l:icon src="${icon}" class="jenkins-avatar" />
+        <l:icon src="${icon}" class="${action.class.name == 'jenkins.model.navigation.UserAction' ? 'jenkins-avatar' : ''}"/>
         <span class="jenkins-visually-hidden" data-type="action-label">${action.displayName}</span>
         <j:if test="${badge != null}">
           <span class="jenkins-badge jenkins-!-${badge.severity}-color" />