Remove unused FLAG_ROTATION_BUTTON_VISIBLE

The code related to this flag was removed in [1], but the flag
declaration, and two no-op usages were left over.

  [1]: I1de7fa061a6c6aba9f949a0bcf8cfced84273e3f

Flag: EXEMPT cleanup
Test: n/a
Bug: 366129400
Change-Id: If3d0751e0a9035ba8b0c66250df9339856788171
1 file changed