Update currency.ts

[eltjehelene]

Changes

• @timgl Probably broke something, but tried to use the documentation from exchangerateapis to update the exchange rates

Checklist

• [x] Titles are in sentence case
• [x] Feature names are in title case
• [x] Words are spelled using American English
• [x] I have checked out our style guide

[charlescook-ph]

@timgl this one has been superseded right?