fix(ci): correct local content source url in Antora playbook (#18)

Change `url: .` to `url: ./../` for the local content source. Antora
resolves bare `..` paths from CWD rather than the playbook directory,
but dot-prefixed paths (`./../`) resolve relative to the playbook file.
Since the playbook is in `docs/`, `./../` correctly resolves to the
repository root where the `.git` directory exists.

Signed-off-by: jimisola <jimisola@jimisola.com>
Co-authored-by: Jimisola Laursen <jimisola.laursen@resurs.se>

Author: jimisola

docs/antora-playbook.yml

@@ -10,7 +10,7 @@ site:
 
 content:
   sources:
-    - url: .
+    - url: ./../
       branches: HEAD
       start_path: docs
     - url: https://github.com/reqstool/reqstool-client