Fix dependency installation in workflow and in the docs

Author: hermanzdosilovic

.github/workflows/docs.yml

@@ -29,7 +29,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -e [docs]
+        pip install -e .[docs]
 
     - name: Build documentation
       run: sphinx-multiversion docs/source docs/build/html --keep-going --no-color

docs/source/contributors_guide/contributing.rst

@@ -24,7 +24,7 @@ Preparing the development setup
 
 .. code-block:: console
 
-    $ pip install -e [dev]
+    $ pip install -e .[dev]
     $ pre-commit install
 
 Building documentation