[HOLD][Odometer] Improvement to DiscardChangesConfirmation usage

[Julesssss]

Problem

We have a Odometer project PR here. A remaining improvement suggestion is an improvement to our usage of DiscardChangesConfirmation modal within the Odometer expense flow.

Replace the isEnabled prop approach in DiscardChangesConfirmation with the existing isSaved flag pattern used in IOURequestStepMerchant

We are partly blocked by this PR which modifies DiscardChangesModal. So this task is being created as a seperate follow up issue.

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[jakubkalinski0]

Update: I am actively observing the blocking PR and will start working on this issue when it's merged.

[jakubkalinski0]

Still waiting for the blocking PR

[jakubkalinski0]

Still waiting