Fix configuration-codesigning.md

[juanmacoo]

• Fix IAM policy formatting to add required Resource
• Fix condition StringEquals syntax

Syntax on both code snippets in Configure IAM policies section under the Code Signing Configuration documentation have syntax issues.

I want to note that the conditional in the documentation is either incorrect or misleading because the resource lambda:codeSigningConfig is not a supported condition key for lambda:CreateFunction as shown here https://docs.aws.amazon.com/service-authorization/latest/reference/list_awslambda.html#awslambda-actions-as-permissions

Issue #, if available:

Description of changes:

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[devlinbd2]

Thank you for providing the corrections to the policy statements.