GitLab

Remove variable from documentation that are now globally defined.

See merge request omegacen/ci-templates!30

Since GitLab 13.1 has introduced
[Global CI variables](https://docs.gitlab.com/ee/api/instance_level_ci_variables.html),
there is no need to add them to each project separately anymore.

Add CONDA_PACKAGE_VERSION variable

See merge request omegacen/ci-templates!29

This variable can be used for setting the conda package name to the
git branch. If it is left unset, it will default to CI_COMMIT_REF_NAME
with bad characters replace with dots ('.'). The bad characters are
conda-build specific, and are '=@#$%^&*:;"\'\\|<>?/ -'
(see https://github.com/conda/conda-build/blob/ef6e0b5aaa7652d37e8cdf3f461bf987610b89b0/conda_build/metadata.py#L529).

CI_COMMIT_REF_NAME is equal to the name of the branch when no tag is
set, and equal to the name of the tag otherwise.

This is documented in https://pkg.go.dev/mod/github.com/bmatcuk/doublestar@v1.2.2