[Web] Minor lang fix

data/web/lang/lang.en.json

@@ -423,7 +423,7 @@
         "targetd_relay_domain": "Target domain %s is a relay domain",
         "temp_error": "Temporary error",
         "text_empty": "Text must not be empty",
-        "tfa_token_invalid": "TFA Token invalid",
+        "tfa_token_invalid": "TFA token invalid",
         "tls_policy_map_dest_invalid": "Policy destination is invalid",
         "tls_policy_map_entry_exists": "A TLS policy map entry \"%s\" exists",
         "tls_policy_map_parameter_invalid": "Policy parameter is invalid",
@@ -913,7 +913,7 @@
         "set_tfa": "Set two-factor authentication method",
         "start_u2f_validation": "Start validation",
         "tfa": "Two-factor authentication",
-        "tfa_token_invalid": "TFA Token invalid",
+        "tfa_token_invalid": "TFA token invalid",
         "totp": "Time-based OTP (Google Authenticator, Authy, etc.)",
         "u2f": "U2F authentication",
         "waiting_usb_auth": "<i>Waiting for USB device...</i><br><br>Please tap the button on your USB device now.",