Before calling a spec stale, check the remote branch, not the local one

I was checking whether a deleted helper function still appeared in a docs spec, and ran git grep against the local develop branch of the docs repo. It still listed the function, so I nearly concluded the code removal had gone ahead of the spec. The docs PR that removed it had merged two days earlier, and the local branch was just behind. Run git fetch first and grep origin/<branch>, or ask gh pr view for the merge state. Separately, when a provided-header change breaks old submissions, build with the grader's Makefile and comment out the failing call to check that it is the only error before reporting the cause.