Fix typo in legacy authentication strategy description.

core/src/main/resources/hudson/security/LegacyAuthorizationStrategy/help.html

 <div>
   Behaves exactly the same as Jenkins &lt;1.164. Namely, if you have the "admin" role,
-  you'll be granted full control over the system, and otherwise (including anonyomus
+  you'll be granted full control over the system, and otherwise (including anonymous
   users) you'll only have the read access.
-</div>
\ No newline at end of file
+</div>