Fix: Reset Replace input field correctly

[badasswp]

This PR resolves this issue.

Description / Background Context

At the moment, when a user performs a search and replace operation and then proceeds to exit the modal, we can see that the replace field still retains the previous value. The expected behaviour should be that this is reset to an empty string.

This PR introduces change to address this issue.

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Testing Instructions

• Pull PR to local.
• Build correctly using yarn build.
• Perform a search & replace activity for any text on your block editor.
• Close the modal and save your post.
• Open search & replace modal.
• Observe that the Replace field is reset to an empty string.
• Observe that there are no regressions introduced as a result of this change.