awscli: 1.14.50 -> 1.15.10; fix build

As reported in #39676 the build broke because of ca52152a as the bump of
`pythonPackages.botocore` to 1.10.9 clashed with the wanted dependencies
in `awscli`.

In order to reduce the risk of accidental bugs because of loosened
version constraints I bumped the AWS CLI to `1.15.10` which depends on
`botocore@1.10` as well.

Fixes #39676