Fix Product kit landing page

[kelliedesigner]

Based on user testing feedback:

• It was unclear why the development standards had a hyperlink but not the other two bullet points

• It was thought that page templates were part of the Design System, not unique to the Product kit

• Reword the Lede 'Design, prototype and build your product using page templates'

• Remove the word 'development' from standards

• Reword Signpost Link to 'View the Product kit (External)

• Make sure Product kit is always written in sentence case in the DS