chore(codebuild): migrate tests to use the Assertions module (#18607)

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Author: skinny85

packages/@aws-cdk/aws-codebuild/package.json

@@ -83,7 +83,7 @@
   },
   "license": "Apache-2.0",
   "devDependencies": {
-    "@aws-cdk/assert-internal": "0.0.0",
+    "@aws-cdk/assertions": "0.0.0",
     "@aws-cdk/aws-sns": "0.0.0",
     "@aws-cdk/aws-sqs": "0.0.0",
     "@aws-cdk/cdk-build-tools": "0.0.0",