Fixes #10534. Reenable the DB settings cache after the schema check.

If mytharchive was the last plugin loaded, it accidentally left the DB
settings cache disabled.  This could be very noticeable when loading
the Watch Recordings screen.
(cherry picked from commit bbd0880)

mythplugins/mytharchive/mytharchive/main.cpp

@@ -324,7 +324,7 @@ int mythplugin_init(const char *libversion)
                 "Couldn't upgrade database to new schema, exiting.");
         return -1;
     }
-    gContext->ActivateSettingsCache(false);
+    gContext->ActivateSettingsCache(true);
 
     ArchiveSettings settings;
     settings.Load();