Fix typo in InternalAuthenticationServiceException javadoc

core/src/main/java/org/springframework/security/authentication/InternalAuthenticationServiceException.java

@@ -17,7 +17,7 @@ package org.springframework.security.authentication;
  * Thrown if an authentication request could not be processed due to a system problem that occurred internally. It
  * differs from {@link AuthenticationServiceException} in that it would not be thrown if an external system has an
  * internal error or failure. This ensures that we can handle errors that are within our control distinctly from errors
- * of other systems. The advantage to this distinction is that the unrusted external system should not be able to fill
+ * of other systems. The advantage to this distinction is that the untrusted external system should not be able to fill
  * up logs and cause excessive IO. However, an internal system should report errors.
  * </p>
  * <p>