docs: fix tabs

Author: maniaba

user_guide_src/source/changelogs/v4.5.6.rst

@@ -23,7 +23,7 @@ Changes
 *******
 
 - **Validation:** Rule ``is_unique`` and ``is_not_unique`` now accept an optional
- ``dbGroup`` as parameter.
+  ``dbGroup`` as parameter.
 
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 Deprecations