Fix minor typo in javadocs.

core/src/main/java/hudson/tasks/UserAvatarResolver.java

@@ -64,7 +64,7 @@ public abstract class UserAvatarResolver implements ExtensionPoint {
      *
      * <p>
      * When multiple resolvers are installed, they are consulted in order and
-     * the search will be over when an avatar is found by someoene.
+     * the search will be over when an avatar is found by someone.
      *
      * <p>
      * Since {@link UserAvatarResolver} is singleton, this method can be invoked concurrently