feat(sidebars): remove 'Common MIME Types', rename main page

[bsmth]

Summary

This PR removes the "Common MIME Types" page in favor of consolidating information into the 'main" guide page for this.

Problem

A standalone page is being deleted and incorporated into a main guide page.

Solution

Remove the nav item for the deleted page.

Changes:
The following page is renamed:

• 'Introduction to MIME types' -> 'Media types (MIME types)'

Screenshots

Before

In the deletion PR preview:

https://pr34269.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types

After

How did you test this change?

1. Checkout Fold common MIME types article into MIME types content#34269
2. yarn && yarn dev
3. localhost:3000

Related issues and pull requests:

• Fold common MIME types article into MIME types content#34269

[bsmth]

I'm going to close for now and revisit when I get back to MIME type / media types doc