Remove clause suggesting absolute paths don't work

Dependencies

• [2] Q2E4J3PH Update docs
• [3] JD6K3NS4 Use absolute path in example as it seems to be working now

Change contents

• edit in doc/manual/src/configuration.md at line 30
  [2.780]→[2.780:859](∅→∅)
  −

  − Note that the included files must be relative to `hydra.conf` (not absolute).