Remove colors.xml file from core/res/res/values-watch/

The colors in values-watch affect the priority in which the color
values are read (in relation to the colors in values/). To keep the
watch colors at the same priority as the ones in values/, we're
removing the values in values-watch/ and providing an watch-specific
overlay for values/.

Bug: 348563872
Test: atest RemoteViewsThemeColorsTest
Flag: EXEMPT, xml config flagging not supported
Change-Id: Ie2e960043fbc947b7d313dd2d3d8acb43545ebeb