[Perl/perl5] ce7890: [doc] Update File::Copy synopsis

[Elvin Aslanov via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: ce789034b8334f0287b20cd30ee2b8859ec79ca9
      
https://github.com/Perl/perl5/commit/ce789034b8334f0287b20cd30ee2b8859ec79ca9
  Author: Elvin Aslanov <rwp.prim...@gmail.com>
  Date:   2022-08-30 (Tue, 30 Aug 2022)

  Changed paths:
    M lib/File/Copy.pm

  Log Message:
  -----------
  [doc] Update File::Copy synopsis

Add `my` to examples for better practice.