Remove `Chapters' directory from template directory used to build
Spanish manuals using texinfo soure files.
- Chapter definitions inside manuals are set interactively through
translation markers. There is no need to have one
language-specific template for each chapter definition. Instead,
we provide one chapter definition template file (e.g., the
`Texinfo/Templates/en_US/Chapters/chapter.texinfo' file).
- Translation markers inside chapter definition template are
expanded when new chapters are created.