The easiest way: download this file pinboard.1.0.8-functions_mod.zip and go to yoursiteaddress/wp-admin/theme-install.php and install this zip (do not unzip this file). Changes made by my: only this missing line. I didn't test it, but it should works. Do it on your own risk.
If you don't want to do this, you can go to yoursiteaddress/wp-admin/theme-editor.php, chose Pinboard, then chose from the right side functions.php and then you have to find (CTRL+F - web browser should manage with this) this line:
wp_register_script( 'ios-orientationchange-fix', get_template_directory_uri() . '/scripts/ios-orientationchange-fix.js', false, null );
hit enter at the end of this line and add:
wp_register_script( 'jquery-migrate', get_template_directory_uri() . '/scripts/jquery-migrate.js', array( 'jquery' ), null );
Then save this file (button is below this window).
Let us know what is the result and witch metod did you choose.
Sorry for my poor english...