Bug 1881845 - Remove nsContentCID.h r=smaug,media-playback-reviewers,karlt

All of these components have been converted to static registration, making this
file unneeded.

Differential Revision: https://phabricator.services.mozilla.com/D202633

dom/html/HTMLTextAreaElement.cpp

@@ -19,7 +19,6 @@
 #include "mozilla/TextControlState.h"
 #include "nsAttrValueInlines.h"
 #include "nsBaseCommandController.h"
-#include "nsContentCID.h"
 #include "nsContentCreatorFunctions.h"
 #include "nsError.h"
 #include "nsFocusManager.h"