docs: make uppercase letters in title lower

Author: kenjis

user_guide_src/source/libraries/validation.rst

@@ -475,7 +475,7 @@ at least 6 characters."
 
 .. note:: When using label-style error messages, if you pass the second parameter to ``setRules()``, it will be overwritten with the value of the first parameter.
 
-Translation Of Messages And Validation Labels
+Translation of Messages and Validation Labels
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 To use translated strings from language files, we can simply use the dot syntax.