EZP-23474: fix LegacyEmbedScriptCommand doesn't activate the LegacyBundles

https://jira.ez.no/browse/EZP-23474
I don't changed it because of performance impact.
Single/double quotes should not be mixed:
https://github.com/ezsystems/ezpublish-kernel/pull/1035#discussion_r18941675
Everywhere in the method single quotes are used