fix(topology/algebra/infinite_sum): add a hint to speed up elaboration (#1824)
fix(topology/algebra/infinite_sum): add a hint to speed up elaboration (#1824)

Fix suggested by Joe on Zulip.

Co-authored-by: mergify[bot] <b09a6ee808b67e98a221404e7aaa52e0398a4954@users.noreply.github.com>

leanprover-community/mathlib,leanprover-community/mathlib