.oniro-ci: remove rules from .bitbake-workspace

Apparently those rules clash with the rules defined in the
.gitlab-ci.yml .workspace-rules, due to the order of evaluation inside
GitLab.

The set of rules on .bitbake-workspace is entirely redundant, and should
be defined by the workflow. The rules on .workspace-rules have a
different purpose, namely to inject specific variables into certian
types of pipelines.

Fixes: #613



Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>