Fix: Default app name on 'About' page is always 'Zuun'

[bmo-at-a9s]

Description

I removed a line likely left in as a debug test during development of cloudfoundry/stratos#4842, which always set the product name on the 'About' page of Stratos to 'Zuun'.
I also took this chance to add an appropriate piece of missing documentation for the feature of being able to use angular customizations to add an arbitrary appName.

Motivation and Context

The change was mistakenly included in #4
Sorry for that, my bad.

How Has This Been Tested?

I started up Stratos locally and made sure that once this line is removed, the app name defaults to Stratos.
Furthermore I also tested that if you use the Customization Service, you can put any name you want and it'll show up.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Docs update
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have followed the guidelines in CONTRIBUTING.md, including the required formatting of the commit message

[wayne]

LGTM.

[norman-abramovitz]

https://github.com/cloudfoundry-community/stratos/releases/tag/v4.8.1-rc.7 should have your change in it.