#837: fix language key for mensa note

Author: jgrobelski

src/assets/i18n/en.json

@@ -315,7 +315,7 @@
       "disclaimer": "All data is used with the kind support of the Studentenwerk Potsdam.",
       "mensaClosed": "This canteen is closed at the moment.",
       "foodhopperGriebnitzsee": "The Food Hopper located at Stahnsdorfer Str. 140-156 is open and offers warm lunches for takeaway.",
-      "mensaAPINotAvailable": "The data are not available for the University of Potsdam anymore. The Studentenwerk Potsdam has developped an own application and provides the menu under this link: ",
+      "mensaAPINotAvailable": "The data is not available for the University of Potsdam anymore. The Studentenwerk Potsdam has developed an own application and provides the menu under this link: ",
       "mensaLinktext": "Web Menu",
       "ulfscafe": "Ulfs Coffee shop",
       "mensen": "canteens"