Use base64 strings for incoming message cache instead of binary

js/modules/migrate_to_sql.js

@@ -86,6 +86,11 @@ async function migrateToSQL({
         forEach(array, item => {
           // In the new database, we can't store ArrayBuffers, so we turn these two fields
           //   into strings like MessageReceiver now does before save.
+
+          // Need to set it to version two, since we're using Base64 strings now
+          // eslint-disable-next-line no-param-reassign
+          item.version = 2;
+
           if (item.envelope) {
             // eslint-disable-next-line no-param-reassign
             item.envelope = arrayBufferToString(item.envelope);