Fix translations

exam/dist/locales/en/translation.json

@@ -1,15 +1,13 @@
 {
-  "": "",
-
   "NotFound_user:login": "User does not exist",
-  "Unauthorized:login": "Invalid e-mail or password",
+  "Unauthorized:login": "Invalid email or password",
 
   "GuestBook": "GuestBook",
 
-  "E-Mail": "E-Mail",
+  "Email": "Email",
   "Password": "Password",
 
-  "E-Mail required": "E-mail required",
+  "Email required": "Email required",
   "Password required": "Password required",
 
   "Log in": "Log in",