[DocsUI M3] Update color values for SDK v30

* For some colors which we can't use color attributes
  directly, use static colors for v30, only
  use dynamic tokens for v31 and above.
* Remove some unused colors.
* Remove unnecessary SDK >= 29 check given the min SDK
  is 30 now.

Bug: 402240208
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: Ibb9ad92b5380afb25523aefd79f04e37f33d812a