Fix more peerDependencies issues

[ndelangen]

We found that:

 WARN  Issues with peer dependencies found
.
└─┬ @storybook/react-webpack5 7.0.0-alpha.60
  └─┬ @storybook/preset-react-webpack 7.0.0-alpha.60
    ├── ✕ missing peer jest-specific-snapshot@^7.0.0
    └── ✕ missing peer require-from-string@^2.0.2
Peer dependencies that should be installed:
  jest-specific-snapshot@^7.0.0  require-from-string@^2.0.2     

..happens when installing storybook 7.0-alpha.60, in a webpack project.

What i did

I removed these dependencies, because according to depcheck they are not needed at all:

(tech/peer-dep-attempt)⚡ % npx depcheck                                                ~/Projects/Storybook/core/code/presets/react-webpack
Unused dependencies
* @babel/preset-flow
* @storybook/react
Unused devDependencies
* @types/util-deprecate
* jest-specific-snapshot

[ndelangen]

Thank you @valentinpalkovic for quick review ❤️