Bug#37400: mysql: Bad help message for charset command

Typo existed in help-text for command "charset" in mysql
client, making the parameter-name different for long and
short forms of the command for no good reason.

Fixed.

client/mysql.cc:
  Make parameter-name in help-text the same for
  long and short forms, for consistency.

client/mysql.cc

@@ -2832,7 +2832,7 @@ com_charset(String *buffer __attribute__((unused)), char *line)
   param= get_arg(buff, 0);
   if (!param || !*param)
   {
-    return put_info("Usage: \\C char_setname | charset charset_name", 
+    return put_info("Usage: \\C charset_name | charset charset_name", 
 		    INFO_ERROR, 0);
   }
   new_cs= get_charset_by_csname(param, MY_CS_PRIMARY, MYF(MY_WME));