Upgrade match-at and flow versions to resolve the match-at flow
errors, allowing us to remove match-at from the .flowconfig ignore
Test plan:
run `jest` and get the following output:
PASS test/unicode-spec.js
PASS test/errors-spec.js
PASS test/mathml-spec.js
PASS test/katex-spec.js (5.104s)
run `flow` and get:
No errors!