Add tix to package requirements for Ubuntu

[spham-amzn]

Change summary

Adding the tix package as an ubuntu package dependency to support the GUI for project export.

### Submission Checklist:

• [X ] Descriptive active voice - Do descriptive sentences have a clear subject and action verb?
• [X ] Answer the question at hand - Does the documentation answer a what, why, how, or where type of question?
• [X ] Consistency - Does the content consistently follow the Style Guide?
• [X ] Help the user - Does the documentation show the user something meaningful?