Bump version of indexmap (#2050)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/2050

X-link: https://github.com/facebook/buck2/pull/575

ocamlrep needs this package updated to a more recent version to build correctly.

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Reviewed By: huydhn, jurajh-fb

Differential Revision: D54091494

fbshipit-source-id: 0486c8d71cd2e990dccd52da33345b17cbdb2e7d