Remove dependency credential test

- the change in CDN results in these tests failing, because the new CDN config does not support credentials in this way.
- we believe that consumers do not use this feature, as we have not had any reports of this causing failures for consumers.
- if we get reports that consumers cannot download dependencies from the CDN with credentials, and we deem this to be a necessary feature, we can update the CDN config and re-add these tests.

src/ruby/brats/brats_test.go

@@ -14,7 +14,6 @@ var _ = Describe("Ruby buildpack", func() {
 	bratshelper.StagingWithBuildpackThatSetsEOL("ruby", func(_ string) *cutlass.App {
 		return CopyBrats("3.1.x")
 	})
-	bratshelper.StagingWithCustomBuildpackWithCredentialsInDependencies(CopyBrats)
 	bratshelper.DeployAppWithExecutableProfileScript("ruby", CopyBrats)
 	bratshelper.DeployAnAppWithSensitiveEnvironmentVariables(CopyBrats)
 	bratshelper.ForAllSupportedVersions("ruby", CopyBrats, func(rubyVersion string, app *cutlass.App) {