Doc: corrected doc QString::operator[]

Task-number: QTBUG-43337
Change-Id: I379dfe3f6909de5a63a67261834ea0edff875f9d
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Martin Smith <martin.smith@digia.com>

src/corelib/tools/qstring.cpp

@@ -4797,11 +4797,11 @@ QString QString::trimmed_helper(QString &str)
 \overload operator[]()
 
 Returns the character at the specified \a position in the string as a
-modifiable reference. Equivalent to \c at(position).
+modifiable reference.
 */
 
 /*! \fn const QChar QString::operator[](uint position) const
-
+    Equivalent to \c at(position).
 \overload operator[]()
 */