style: format code with Prettier

This commit fixes the style issues introduced in 0f494d0 according to the output
from Prettier.

Details: None

packages/main/src/AuthenticationService.ts

@@ -20,7 +20,7 @@ export class AuthenticationService {
    */
   authenticateUser(username: string, password: string): number {
     const user = userCredentials.find(
-      (user) => user.username === username && user.password === password
+      (user) => user.username === username && user.password === password,
     );
 
     return user ? user.customerId : -1;