"as necessary to provide the Service, including improving the Service over time."
"This license does not grant GitHub the right to sell Your Content" is unambiguously clear.
I'm not sure I agree that anything expressed in a legal contract using natural language is "unambiguously clear". MS / Github's expensively-attired lawyers will not doubt forcefully argue that they are not selling the YOUR content, but a service based on a model generated from a large collection of content, which they have been granted a licence to "parse it into a search index or otherwise analyze it on our servers". There may even be in-court discussion of generalization, which will be exciting.