Change wording in i18n texts

aleksis/apps/chronos/frontend/messages/de.json

@@ -27,8 +27,8 @@
     },
     "substitutions": {
       "overview": {
-        "menu_title": "Vertretungsstunden planen",
-        "title_plural": "Vertretungsstunden planen",
+        "menu_title": "Vertretungen planen",
+        "title_plural": "Vertretungen planen",
         "filter": {
           "groups": "Nach Gruppen filtern"
         },

aleksis/apps/chronos/frontend/messages/en.json

@@ -45,8 +45,8 @@
     },
     "substitutions": {
       "overview": {
-        "menu_title": "Plan substitution lessons",
-        "title_plural": "Plan substitution lessons",
+        "menu_title": "Plan substitutions",
+        "title_plural": "Plan substitutions",
         "info_alert": {
           "text": "This page shows all lessons that collide with known absences of their respective teachers.",
           "button": "Manage absences"