feature symfony#6949 Update ProgressBar docs with regress information (jameshalsall)

This PR was squashed before being merged into the master branch (closes symfony#6949).

Discussion
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Update ProgressBar docs with regress information

Doc updates for changes introduced in symfony/symfony#19824

Commits
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d3346d8 Update ProgressBar docs with regress information

Author: xabbuh

components/console/helpers/progressbar.rst

@@ -35,6 +35,12 @@ number of units, and advance the progress as the command executes::
     // ensure that the progress bar is at 100%
     $progress->finish();
 
+.. tip::
+
+    You can also regress the progress bar (i.e. step backwards) by calling
+    ``$progress->advance()`` with a negative value. For example, if you call
+    ``$progress->advance(-2)`` then it will regress the progress bar 2 steps.
+
 Instead of advancing the bar by a number of steps (with the
 :method:`Symfony\\Component\\Console\\Helper\\ProgressBar::advance` method),
 you can also set the current progress by calling the