[no-Jira] Do not combine spouse's approved MHA amounts

[canac]

Description

My understanding is that the current approved MHA amount is the same for both staff so that if one of them passes away their approved MHA doesn't go down. This PR fixes the MHA card to use the approved amount directly instead of adding them together. It also renames some fields for consistency and clarity and fixes a couple localized strings.

@dr-bizz I'd love to get your approval on this PR to make sure that I'm understanding what the HCM API returns correctly.

Testing

• Go to step 2 of a salary calculation
• Check that the approved MHA amount is one spouse's approved amount not the sum of both spouses

Checklist:

• I have given my PR a title with the format "MPDX-(JIRA#) (summary sentence max 80 chars)"
• I have applied the appropriate labels (Add the label "Preview" to automatically create a preview environment)
• I have run the Claude Code /pr-review command locally and fixed any relevant suggestions
• I have requested a review from another person on the project
• I have tested my changes in preview or in staging
• I have cleaned up my commit history

[github-actions]

Preview branch generated at https://mha-card-improvements.d3dytjb8adxkk5.amplifyapp.com

[github-actions]

Bundle sizes [mpdx-react]

Compared against c793717

No significant changes found