Update ketting to the latest version #142

[syedfkabir]

Resolves #142

Changes

• upgraded ketting dependency from 7.3.0 to 7.5.0.

Testing

• tested most of the a12n and media-api routes to see if anything broke
• tested this issue again https://github.com/curveball/a12n-server/issues/420 and it was resolved