Removed obsolete bit of text about case-sensitive regular expressions.

Docs/manual.texi

@@ -12761,12 +12761,6 @@ example, @samp{x*} matches any number of @samp{x} characters,
 @samp{[0-9]*} matches any number of digits, and @samp{.*} matches any
 number of anything.
 
-@item
-Regular expressions are case sensitive, but you can use a character class to
-match both lettercases if you wish.  For example, @samp{[aA]} matches
-lowercase or uppercase @samp{a} and @samp{[a-zA-Z]} matches any letter in
-either case.
-
 @item
 The pattern matches if it occurs anywhere in the value being tested.
 (SQL patterns match only if they match the entire value.)