fix(addon-storyshots): Remove excess slashes from jest transform warning

[callumacrae]

It's printing all of them, so I copied all of them, and that didn't work!

before:

What I did

How to test

Testable by running storyshots tests with this config:

import initStoryshots, { multiSnapshotWithOptions } from '@storybook/addon-storyshots';

initStoryshots({
  test: multiSnapshotWithOptions()
});

Then if you're using CSFs, the warning will be thrown.

The example in the docs is already correct.

[vercel]

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[shilman]

💯