[DESIGN] Update last name help text on Mobility Pass form to indicate case sensitivity

[thekaveman]

There is concern from SBMTD that the existing help text on the Mobility Pass form is not clear enough about the case-sensitivity of the Last name field, currently:

The suggested copy change for the highlighted text is:

This form is case sensitive.

Acceptance Criteria

• English copy is finalized
• English copy is translated to Spanish
• The updated copy for both languages appears on the Mobility Pass form

[thekaveman]

@indexing initial assignment for you to finalize the English copy and get it translated to Spanish.

[indexing]

If we make this change for SBMTD, we need to evaluate making the change for MST as well.

[indexing]

@srhhnry is revisiting this form view, so I'm reassigning for the design phase.