[Sb refactor] Remove debug color flags

`NEW_STATUS_BAR_ICONS_DEBUG_COLORING` was implemented to help us
distinguish the icons coming from the new pipeline vs the old one. Now
that we are fully rolled out, we don't need this flag.

Fixes: 260881289
Test: tests in com.android.systemui.statusbar.pipeline
Test: manual
Change-Id: Ia3691744e9d00fc41a041c4aaa032dce23cc6e22