[Perl/perl5] caef5a: .lgtm.yml: Delete obsolete file

[Elvin Aslanov via perl5-changes]

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: caef5a7dffddb63ccd397171f834d8f5122356ee
      
https://github.com/Perl/perl5/commit/caef5a7dffddb63ccd397171f834d8f5122356ee
  Author: Elvin Aslanov <rwp.prim...@gmail.com>
  Date:   2023-07-18 (Tue, 18 Jul 2023)

  Changed paths:
    R .lgtm.yml
    M MANIFEST

  Log Message:
  -----------
  .lgtm.yml: Delete obsolete file

Fixes #21252