Maintenance: mention removal of --no-dll flag

[konsalex]

--no-dll flag is removed in v7

Issue:

What I did

Remove the --no-dll flag from v7 docs

How to test

• Is this testable with Jest or Chromatic screenshots?
• Does this need a new example in the kitchen sink apps?
• Does this need an update to the documentation?

If your answer is yes to any of these, please make sure to include it in your PR.

[yannbf]

Hey @konsalex thanks a lot for your contribution! There are more places where dll is used, could you perhaps remove their references too?

• Remove this additional reference in the docs
• Remove types here
• Add an entry in MIGRATION.md in the Storybook section that the DLL options got removed. Use this as reference https://github.com/storybookjs/storybook/blob/next/MIGRATION.md#deprecated-dll-flags

[konsalex]

Hey @yannbf , fixed the points you've mentioned

[yannbf]

Thank you so much @konsalex ! <3