Remove unused text, no need to translate it anymore.

i18n/en.i18n.json

@@ -325,7 +325,6 @@
     "welcome-list2": "Advanced",
     "what-to-do": "What do you want to do?",
     "admin-panel": "Admin Panel",
-    "system-setting": "System Setting",
     "settings": "Settings",
     "people": "People",
     "registration": "Registration",
@@ -345,4 +344,4 @@
     "email-invite-register-subject": "__inviter__ sent you an invitation",
     "email-invite-register-text": "Dear __user__,\n\n__inviter__ invites you to Wekan for collaborations.\n\nPlease follow the link below:\n__url__\n\nAnd your invitation code is: __icode__\n\nThanks.",
     "error-invitation-code-not-exist": "Invitation code doesn't exist"
-}
+}