docs(aws-codebuild): Fix module name in README"@aws-cdk/@aws-codepipe…

…line-actions" => "aws-cdk/aws-codepipeline-actions" (aws#23309)

Hi folks,

I believe there is no need in `@` inside in the name of `@aws-cdk/@aws-codepipeline-actions`.

Please let me know if this minor change makes sense.

Thank you
----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-codebuild/README.md

@@ -158,7 +158,7 @@ const project = new codebuild.PipelineProject(this, 'Project', {
 })
 ```
 
-For more details, see the readme of the `@aws-cdk/@aws-codepipeline-actions` package.
+For more details, see the readme of the `@aws-cdk/aws-codepipeline-actions` package.
 
 ## Caching