Merge pull request #5301 from shuujii/fix-typos-in-mruby-presym-disableenable.h

Fix typos in `mruby/presym/{disable,enable}.h` [ci skip]

include/mruby/presym/disable.h

 /**
-** @file mruby/presym/scanning.h - Disable Preallocated Symbols
+** @file mruby/presym/disable.h - Disable Preallocated Symbols
 **
 ** See Copyright Notice in mruby.h
 */

include/mruby/presym/enable.h

 /**
-** @file mruby/presym/scanning.h - Enable Preallocated Symbols
+** @file mruby/presym/enable.h - Enable Preallocated Symbols
 **
 ** See Copyright Notice in mruby.h
 */