Relax ex_aws / hackney restrictions

[Jonatan Männchen]

hackney and ex_aws can not be updated to a new minor version given the current restrictions. THose should be leaxed to allow minor updates.

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~> 1.16.0 => ~> 1.16

[Stéphane Travostino]

I’ve pushed a fork on github relaxing the hackney requirement: https://github.com/punterslounge/belt

Though I would prefer if that fix were to be incorporated in this repository, I’m not a fan of maintaining a git-only dependency.