Install v4.0.0 of aws plugin

[MitchellGerdisch]

Consistency with other language examples and v4 of the AWS SDK is being used.

[marcelbirkner]

Thank you for the fix. Without this PR I am getting the following error for the pulumi_over_http example:

❯ go run main.go
Failed to install program plugins: code: 255
, stdout:
, stderr: [resource plugin aws-3.2.1] installing
error: [resource plugin aws-3.2.1] downloading from : failed to download plugin: aws-3.2.1: 403 HTTP error fetching plugin from https://get.pulumi.com/releases/plugins/pulumi-resource-aws-v3.2.1-darwin-arm64.tar.gz

: failed to install plugin: exit status 255
exit status 1