Update import design schema

[aabidsofi19]

Description

This PR fixes #

• remove Meshery Design as default Type
• replace file name with filename

Notes for Reviewers

Signed commits

• [ ] Yes, I signed my commits.

[welcome[bot]]

Yay, your first pull request! :thumbsup: A contributor will be by to give feedback soon. In the meantime, please review the Layer5 Community Welcome Guide and sure to join the community Slack. Be sure to double-check that you have signed your commits. Here are instructions for making signing an implicit activity while peforming a commit.

[welcome[bot]]

Thanks for your contribution to Meshery! :tada: