fx quant: add docblocks to _find_matches and _find_quants (#43928)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43928
Improving readability, no logic change.
Test Plan:
CI
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D23440249
fbshipit-source-id: a7ebfc7ad15c73e26b9a94758e7254413cc17d29
