chore: fix old aws-sdk-cpp version references

[alex-chew]

Description of changes: I missed some aws-sdk-cpp version references in #589, leaving the in-repo documentation and CI scripts in an inconsistent state. This PR brings those references up to date, so that no old version numbers remain (except in the changelog):

$ rg -g '!.git' --hidden '1\.7\.231'
CHANGELOG.md
8:* aws-cpp-sdk dependency bump to version 1.7.231

$ rg -g '!.git' --hidden '0\.3\.15'

$

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• Were any files moved? Moving files changes their URL, which breaks all hyperlinks to the files.

[dougch]

LGTM