update lang sync - remove old translations (#1751)

scripts/lang-sync.ts

@@ -1,6 +1,7 @@
-
 /**
- * Script to copy new english translation strings to the other language files
+ * Script to:
+ * - copy new english translation strings to the other language files
+ * - remove old translation strings from the other language files
  */
 
 import * as fs from 'fs-extra';
@@ -18,11 +19,19 @@ for (const lang of langFiles) {
   const translationStrings = fs.readJsonSync(langPath);
 
   if (lang !== 'en.json') {
+    // find any keys in the main file that are not in the translation file, and add
     for (const [key, value] of Object.entries(main)) {
       if (!translationStrings.hasOwnProperty(key)) {
         translationStrings[key] = value;
       }
     }
+
+    // find any keys in the translation file that are not in the main file, and remove
+    for (const key of Object.keys(translationStrings)) {
+      if (!main.hasOwnProperty(key)) {
+        delete translationStrings[key];
+      }
+    }
   }
 
   // sort keys