Fix typo in resource server documentation

Author: eleftherias

docs/manual/src/docs/asciidoc/_includes/servlet/oauth2/oauth2-resourceserver.adoc

@@ -718,8 +718,8 @@ public JwtAuthenticationConverter jwtAuthenticationConverter() {
     JwtGrantedAuthoritiesConverter grantedAuthoritiesConverter = new JwtGrantedAuthoritiesConverter();
     grantedAuthoritiesConverter.setAuthoritiesClaimName("authorities");
 
-    JwtAuthenticationConverter authenticationConverter = new JwtAuthenticationConverter();
-    jwtAuthenticationConverter.setJwtGrantedAuthoritiesConverter(authoritiesConverter);
+    JwtAuthenticationConverter jwtAuthenticationConverter = new JwtAuthenticationConverter();
+    jwtAuthenticationConverter.setJwtGrantedAuthoritiesConverter(grantedAuthoritiesConverter);
     return jwtAuthenticationConverter;
 }
 ----