Correct typo in app/email.go (#5569)

i18n/en.json

@@ -2192,11 +2192,11 @@
     "translation": "{{ .SiteName }} Team Setup"
   },
   {
-    "id": "api.templates.singin_change_email.body.info",
+    "id": "api.templates.signin_change_email.body.info",
     "translation": "You updated your sign-in method on {{ .SiteName }} to {{.Method}}.<br>If this change wasn't initiated by you, please contact your system administrator."
   },
   {
-    "id": "api.templates.singin_change_email.subject",
+    "id": "api.templates.signin_change_email.subject",
     "translation": "[{{ .SiteName }}] You updated your sign-in method on {{ .SiteName }}"
   },
   {