Errors using non-ASCII characters for singular & plural 

# Bug report

Configuring a list with:

```
label:`Παραγγελίες`,
singular: "Παραγγελία(this is the singular)",
plural: 'Παραγγελίες (this is the plural)',
```
Results in the following error:

```
GraphQLError [Object]: Syntax Error: Cannot parse the unexpected character "\u03A0".

```
See original post in Slack:
https://keystonejs.slack.com/archives/C01RWRZFS6A/p1619073400090900

