Add force-update to release update docs

[MyPyDavid]

Sometimes --force-reinstall is needed to upgrade patch release in a current installation

rdmorganiser/rdmo#886 (comment)

[MyPyDavid]

Most of the dependencies in the pyproject.toml (like "django>=4.2,<5.0",) don't have the patch version specified and will require an extra pip install -U django to be upgraded for new patch releases.

The pip install -U rdmo --force-reinstall command will upgrade those dependencies as well.

Help text for --force-reinstall, from https://pip.pypa.io/en/stable/ux-research-design/research-results/pip-force-reinstall/#recommendations:

Reinstall package(s), and their dependencies, even if they are already up-to-date. Where package(s) are not up-to-date, upgrade these to the latest version (unless version specifiers are used).