Add the census api disclosure to the methodology and data page

[KameronKerger]

Describe the bug As Travis astutely noted, apps that use the census api, per the census terms of service, should display the following: This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.

To Reproduce Steps to reproduce the behavior:

1. Go to 'methodology & data'
2. See error

Expected behavior Add the text between the text and the start of the data boxes.

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context Add any other context about the problem here.