distributed support: fix typo in cmake in headers file list.
distributed support: fix typo in cmake in headers file list.

rdebroiz/dtk,d-tk/dtk,rdebroiz/dtk,rdebroiz/dtk,rdebroiz/dtk,d-tk/dtk,d-tk/dtk,d-tk/dtk,d-tk/dtk,NicolasSchnitzler/dtk,NicolasSchnitzler/dtk,NicolasSchnitzler/dtk,d-tk/dtk,NicolasSchnitzler/dtk