Rename test app

[paulroberttaylor-zz]

For the default 'sfdx force:lightning:test:run' command to work without the --appname flag, there needs to be a Tests.app lightning app.

The current naming results in no tests being run, and the following error in the output: Cannot read property 'endsWith' of undefined.

[cdengSFDC]

The test app name is updated in newer versions of sfdx binary which will be released soon.