Update server/graphql/v1/mutations/expenses.js
Update server/graphql/v1/mutations/expenses.js

update error message

Co-Authored-By: François Hodierne <5187da0b934cc25eb2201a3ec9206c24b13cb23b@hodierne.net>
OpenCollective/opencollective-api,OpenCollective/opencollective-api,OpenCollective/opencollective-api