Fix faulty translation key for covers

src/translations/en.json

@@ -7,7 +7,7 @@
     "all_climates": "All Climates",
     "climates": "Climates"
   },
-  "covers": {
+  "cover": {
     "all_covers": "All Covers",
     "covers": "Covers"
   },

src/translations/nl.json

@@ -7,7 +7,7 @@
     "all_climates": "Alle Klimaatregelingen",
     "climates": "Klimaatregelingen"
   },
-  "covers": {
+  "cover": {
     "all_covers": "Alle Bedekkingen",
     "covers": "Bedekkingen"
   },