Number input boxes for values with Infinity as a default display "Infinity" instead of the infinity symbol

[anth-volk]

This is visible, for example, in IRS income tax bracket 7's upper threshold, which is infinite. Instead of the input displaying ∞, it displays "Infinity". However, if a user sets a value to Infinity when that's not the default (e.g., raising tax bracket 6's threshold), it always displays as ∞.