Remove redundant xxx_dark resource and definition from Docsui

Docsui follow night mode framework to support dark UI visual
It's unnecessary to keep redundant dark resrouces in package
The change could also benefit and minize RRO theme scope

Change-Id: I77eb5d5d0559cc512a07885ebbe5ccfe1bf8d79a
Fix:119619772
Test: atest DocumentsUITests