1007 fixup what FF75+ applies to

user.js

@@ -590,9 +590,9 @@ user_pref("browser.cache.disk.enable", false);
  * [NOTE] This means any permission changes are session only
  * [1] https://bugzilla.mozilla.org/967812 ***/
    // user_pref("permissions.memory_only", true); // [HIDDEN PREF]
-/* 1007: disable media cache from writing to disk in Private Browsing [FF75+]
+/* 1007: disable media cache from writing to disk in Private Browsing
  * [NOTE] MSE (Media Source Extensions) are already stored in-memory in PB */
-user_pref("browser.privatebrowsing.forceMediaMemoryCache", true);
+user_pref("browser.privatebrowsing.forceMediaMemoryCache", true); // [FF75+]
 user_pref("media.memory_cache_max_size", 16384);
 
 /** SESSIONS & SESSION RESTORE ***/