Bugfix - Warning in console regarding stepIndex variable

[matextrem]

What it solves

This PR closes #2429

How this PR fixes it

We added stepIndex property used in FullParagraph as a Transient prop

How to test it

1. Go to create a Safe
2. Navigate through the steps and you won't see any error in console related to stepIndex prop.

[github-actions]

CLA Assistant Lite All Contributors have signed the CLA.

[katspaugh]

🆒

[github-actions]

ESLint Summary View Full Report

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Type	Occurrences	Fixable
Errors	0	0
Warnings	0	0
Ignored	0	N/A

• Result: ✅ success
• Annotations: 0 total

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^{Report generated by eslint-plus-action}

[github-actions]

• Safe Multisig app mainnet

[github-actions]

• Safe Multisig app rinkeby

[katspaugh]

I've tested it and the warning is gone ✅
Thanks Mati!