Clean up redundant git configuration in docs repository

The container image already defines the user and the email for the builder's/CI's git operations[1] so there is no need to override it docs repository CI configuration.

[1]https://gitlab.eclipse.org/eclipse/oniro-core/oniro/-/blob/kirkstone/.oniro-ci/containers/bitbake-builder/Dockerfile

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information