Make images plugin show up in TinyMCE 5
Make images plugin show up in TinyMCE 5

Test Plan:
  - Enable RCE Enhancements
  - Load a page with an RCE
  - You should see the image plugin

Change-Id: I4a23828fec58edbf62ed159ff7621bc7a5854e96
Reviewed-on: https://gerrit.instructure.com/188668
Tested-by: Jenkins
QA-Review: Brent Burgoyne <bccf16d7abdd2611580b1cd7d7a6fcc150d619da@instructure.com>
Product-Review: Brent Burgoyne <bccf16d7abdd2611580b1cd7d7a6fcc150d619da@instructure.com>
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

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