[Fiware-tech-help] [Chp - Security][Identity Management] Fix database.yml example filename

[David Muriel]

On the installation guide, in the instructions for running KeyRock
locally, to configure the database the user is instructed to copy the
database.yml.example file to database.yml and the edit that file. The
filename available on the repository is database.example.yml instead
of database.yml.example as stated on the document.