dt/rpk: remove logging of exception

Instead of logging, assume caller will catch/log the exception to avoid
polluting the log when an exception is ignored.

Signed-off-by: Ivo Jimenez <ivo@redpanda.com>
(cherry picked from commit 9bce021)

tests/rptest/clients/rpk.py

@@ -1135,7 +1135,6 @@ def _execute(self, cmd, stdin=None, timeout=None, log_cmd=True, env=None):
         self._redpanda.logger.debug(f'\n{output}')
 
         if p.returncode:
-            self._redpanda.logger.error(stderror)
             raise RpkException(
                 'command %s returned %d, output: %s' %
                 (' '.join(cmd) if log_cmd else '[redacted]', p.returncode,