Docs: Apply suggestions from CR regarding Poetry example

Author: browniebroke

docs/user/build-customization.rst

@@ -326,10 +326,10 @@ Take a look at the following example:
      jobs:
        post_create_environment:
          # Install poetry
+         # https://python-poetry.org/docs/#installing-manually
          - pip install poetry
          # Tell poetry to not use a virtual environment
          - poetry config virtualenvs.create false
-       post_install:
          # Install dependencies with 'docs' dependency group
          # https://python-poetry.org/docs/managing-dependencies/#dependency-groups
          - poetry install --with docs