Fix typo

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

.tx/config

@@ -4,6 +4,6 @@ lang_map = bg_BG: bg, cs_CZ: cs, fi_FI: fi, hu_HU: hu, nb_NO: nb, sk_SK: sk, th_
 
 [nextcloud.passman-webextension]
 file_filter = _locales/<lang>/messages.json
-source_file = _locales/<lang>/messages.json
+source_file = _locales/en/messages.json
 source_lang = en
 type = CHROME