Remove janky array copying workaround for IE8
Summary:
Internet Explorer 8 and earlier did not consider DOM NodeLists to be JS objects.
In different words: IE<9 did not support Array#slice on collections objects.
See for example https://stackoverflow.com/a/11113539
This reverts rP597c6c07f7120d253e83fa110db8842bfa05859f
Test Plan: Still: Load a diff in a web browser; see changes and do not get JS errors.
Reviewers: O1 Blessed Committers, mainframe98
Reviewed By: O1 Blessed Committers, mainframe98
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D25704