Don't lock aws-cdk-lib version in peerDependencies

[niebloomj]

aws-cdk-lib/core/lib/tag-manager").TagManager'.
npm ERR!               Types have separate declarations of a private property 'tags'.

Right now, the package.json specifies a specific hardcoded version of aws-cdk-lib. This causes the npm update command to crash with the above error. To solve this, the package.json should specify a minimum cdk version with a ^ symbol as opposed to a fixed cdk version