fix incorrect header

Author: Ohasumi

server/auth/types/kerberos/routes.ts

@@ -49,10 +49,13 @@ export class KerberosAuthRoutes {
           user = await this.securityClient.authinfo(request);
         } catch (error) {
           context.security_plugin.logger.error(`Failed authentication: ${error}`);
-          return response.unauthorized({
-            body: `Kerberos authentication failed ${error}`,
-            headers: 'WWW-Authenticate: Negotiate',
-          });
+          return response.unauthorized(
+            {
+              body: `Kerberos authentication failed ${error}`,
+              headers: {
+                'www-authenticate': 'Negotiate',
+              },
+            });
         }
 
         // clear session