Make name unique to fix issue #22426 (#22458)

* make name unique

* delete mini class instead rename

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

public/sass/base/_icons.scss

@@ -19,11 +19,6 @@
   }
 }
 
-.mini {
-  width: 0.8em;
-  height: 0.8em;
-}
-
 .gicon-add-annotation {
   background-image: url('../img/icons_#{$theme-name}_theme/icon_add_annotation.svg');
 }