Trivial tweaks to stop tracking source span directly Firstly, remove some unnecessary work from `sccs_info`. This included debug printing which ends up giving all mir borrowck queries a dependency edge from the query to `source_span` (I think?). Secondly, turn some calls from `hir_span` (which does some span adjustment, and thus incurs span tracking, which causes a dependency edge from the query to `source_span`) to `def_span`, which should cache better. r? oli-obk