bug #5126 Fix a typo in ProgressBar usage example (kamazee)

This PR was submitted for the 2.5 branch but it was merged into the 2.6 branch instead (closes #5126).

Discussion
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Fix a typo in ProgressBar usage example

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.5+
| Fixed tickets | #5125

Docs say `%step%` while the context suggests `%current%` -- looks like a typo.

Commits
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511b7a8 Fix a typo in ProgressBar usage example

Author: wouterj

components/console/helpers/progressbar.rst

@@ -334,4 +334,4 @@ your own::
 For the ``filename`` to be part of the progress bar, just add the
 ``%filename%`` placeholder in your format::
 
-    $bar->setFormat(" %message%\n %step%/%max%\n Working on %filename%");
+    $bar->setFormat(" %message%\n %current%/%max%\n Working on %filename%");