extra: remove commented out 'X' and 'x' formats

These formats are already covered with 'T' | 'X' in line 571 and 'D' | 'x' in
line 446.
auto merge of #9734 : luisbg/rust/master, r=alexcrichton

These formats are already covered with 'T' | 'X' in line 571 and 'D' | 'x' in
line 446.