fix(effects): prevent deadlock in flushing stderr

If tracing is installed, the `warn!` call will attempt to write to `ErrorStream`, which seems to cause a deadlock when we are destroying the `ErrorStream`.

git-branchless-lib/src/core/effects.rs

@@ -829,13 +829,6 @@ trait WriteProgress {
  fn drop(&mut self) {
  let buffer = self.get_buffer();
  if !buffer.is_empty() {
- // In practice, we're expecting that every sequence of `write` calls
- // will shortly end with a `write` call that ends with a newline, in
- // such a way that only full lines are written to the output stream.
- // This assumption might be wrong, in which case we should revisit
- // this warning and the behavior on `Drop`.
- warn!(?buffer, "WriteProgress dropped while buffer was not empty");
-
  // NB: this only flushes completely-written lines, which is not
  // correct. We should flush the entire buffer contents, and possibly
  // force a newline at the end in the case of a progress meter being