fix(storybook): change-storybook-targets should not fail if no build

[mandarini]

Current Behavior

change-storybook-targets generator (and migrator - they are the same) throws an error if there is no target configured for building Storybook.

Expected Behavior

change-storybook-targets generator (and migrator - they are the same) should work even if there is no target set for building Storybook.

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✅ Successfully ran 11 targets

• nx affected --target=e2e --base=40d9901fa53a1c270f2c654b374a8f55f72dab9c --head=c78b245bfe8a25d1f029cfd9ceeba5ac5fdec6cf --exclude=e2e-storybook,e2e-storybook-angular,e2e-react-native,e2e-detox --parallel=1
• nx affected --target=test --base=40d9901fa53a1c270f2c654b374a8f55f72dab9c --head=c78b245bfe8a25d1f029cfd9ceeba5ac5fdec6cf --parallel=1
• nx affected --target=build --base=40d9901fa53a1c270f2c654b374a8f55f72dab9c --head=c78b245bfe8a25d1f029cfd9ceeba5ac5fdec6cf --parallel=3
• nx affected --target=lint --base=40d9901fa53a1c270f2c654b374a8f55f72dab9c --head=c78b245bfe8a25d1f029cfd9ceeba5ac5fdec6cf --parallel=3
• nx-cloud record -- yarn nx workspace-lint
• nx-cloud record -- yarn documentation
• nx build typedoc-theme
• nx-cloud record -- yarn depcheck
• nx-cloud record -- yarn check-commit
• nx-cloud record -- yarn nx format:check --base=40d9901fa53a1c270f2c654b374a8f55f72dab9c --head=c78b245bfe8a25d1f029cfd9ceeba5ac5fdec6cf
• nx-cloud record -- yarn check-imports

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1 Ignored Deployment

Name	Status	Preview	Updated
nx-dev	⬜️ Ignored (Inspect)		Jul 6, 2022 at 1:08PM (UTC)

[meeroslav]

Left one minor comment. Otherwise looks good to me! Thank you!

[github-actions]

This pull request has already been merged/closed. If you experience issues related to these changes, please open a new issue referencing this pull request.