[DocsUI M3] Remove "_m3" version icons for overlayable icons

These overlayable icons should maintain the existing names
(e.g. without "_m3" suffix) otherwise it might break OEM's
RRO icon override. These deleted files will be moved to
RRO instead.

Bug: 427830186
Test: EXEMPT configuration change
Flag: com.android.documentsui.flags.use_material3
Change-Id: I01a19aef1d753ade8fc7274fda3d8e225c933461