chore(leanpkg.toml): Lean 3.7.2c (#2203)
* chore(leanpkg.toml): Lean 3.7.2c
Lean 3.7.1c had a bug that prevented Lean on windows from importing oleans properly (see https://github.com/leanprover-community/lean/pull/155). This is fixed in Lean 3.7.2c.
* update contribute/index.md
