message: remove obsolete keyword 'unsafe'
diff: @@ -158,7 +158,7 @@ impl Heap {
  }
  unsafe impl AllocRef for Heap {
  - unsafe fn alloc(&mut self, layout: Layout) -> Result<(NonNull<u8>, usize), AllocErr> {
  + fn alloc(&mut self, layout: Layout) -> Result<(NonNull<u8>, usize), AllocErr> {
  self.allocate_first_fit(layout)
  }
  