Correct column name in information schema

Correct column name in information schema

Although the standard has routines.result_cast_character_set_name, given
the naming of the surrounding columns, we concluded that this must have
been a mistake and that result_cast_char_set_name was intended, so
change the implementation.  The documentation was already using the new
name.

found by Clément Prévost <prevostclement@gmail.com>