chore(cli-integ): example downloads publib from npm (#28829)

`publib` is our package that includes a CLI tool named `publib-ca`. 

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Author: kaizencc

packages/@aws-cdk-testing/cli-integ/README.md

@@ -77,7 +77,8 @@ $ ./build.sh
 $ ./pack.sh
 
 # Use publib to upload to CodeArtifact
-$ npm install -g publib-ca
+$ npm install -g publib
+# publib-ca is a CLI tool that comes with publib
 $ publib-ca create
 $ publib-ca publish /path/to/dist