feat(cdk-assets): release official GA (#172)

Remove the prerelease tag from `cdk-assets`. This tool is ready to be
used for real.

We are still releasing under the `v3-latest` tag, so CDK Pipelines users
won't automatically switch over to it just yet, but this is sending the
right signal about the tool's stability and fitness for purpose.

---
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under the terms of the Apache-2.0 license

Author: rix0rrr

.github/workflows/release.yml

@@ -627,7 +627,6 @@ const cdkAssets = configureProject(
       },
     ],
     npmDistTag: 'v3-latest',
-    prerelease: 'rc',
     majorVersion: 3,
 
     jestOptions: jestOptionsForProject({