Remove our fallback implementation of Intl.PluralRules

[romaricpascal]

What

Remove our fallback implementation for Intl.PluralRules used by the Character Count. For browsers that do not support Intl.PluralRules, fall back to always using the 'other' translation.

Why

As of GOV.UK Frontend v5.0, JavaScript will only run in browsers that support ES6 modules. The intersection of browsers that support ES6 modules but not Intl.PluralRules is relatively small (Safari 10.3 - 12.5 on iOS, Safari 10.1 - 12.1 on macOS, Edge 16-18, Chrome 61-62 and Opera 48-49) and does not justify the overhead of including the polyfill.

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• We've validated falling back to the 'other' translation is OK
• The fallback implementation is removed

[domoscargin]

As part of this, we should have a glance at our use of Intl.NumberFormat - we use similar guards for the two.

[colinrotherham]

@domoscargin I hadn't realised there was overlap in this GitHub issue

As part of this, we should have a glance at our use of Intl.NumberFormat - we use similar guards for the two.

We handled the Intl.NumberFormat check in this change:

• 20c0d5f Remove hasIntlNumberFormatSupport() check

But loosened Intl.PluralRules (without removing it) in this one:

• dc781d6 Loosen hasIntlPluralRulesSupport() check

Hopefully helpful for when this issue is picked up