[DocsUI M3] Fix "Use this folder" button disabled color

Remove the v31 style override for the button to use the default
disabled button color from Material.

Check the attached bug for the before/after comparison.

Bug: 406104107
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: I0e7caf8ee332690f096a997cd473a881d4c39a7d