Enhance sast-rule python/xml/rule-expatreader.yml
According to gitlab-org/gitlab#434275, this commit improves the detection of a series of features in the XML parsing package. The scope of detection has been expanded according to https://bandit.readthedocs.io/en/latest/blacklists/blacklist_calls.html#b313-b320-xml, which goes beyond the functionality described in the issue, but captures the essence of the existing rule.