Fix BitClust parse error in Kernel#raise sample causing CI failure on Ruby 4.0

[Copilot]

The rake (ubuntu-latest, 4.0) GitHub Actions job failed during static HTML generation due to a syntax error in documentation sample code for Kernel#raise/Kernel#fail. BitClust raised ParseError because a begin/rescue example block was missing its closing end.

• Root cause

  • refm/api/src/_builtin/functions contained an unterminated sample block in the raise/fail section (begin ... rescue without final end).

• Change made

  • Added the missing end immediately after the version-conditional sample output block so the sample is syntactically complete for BitClust parsing.

• Impact

  • Unblocks static HTML generation for version 4.0 (and other CI matrix entries that process the same source).

begin
  open("nonexist")
rescue
#@since 3.4
  raise   #=> 'open': No such file or directory - "nonexist" (Errno::ENOENT)
#@else
  raise   #=> `open': No such file or directory - "nonexist" (Errno::ENOENT)
#@end
end