clean up babel messages when testing

[ericsoderberghp]

When running yarn test, the console shows multiple messages like:

The "loose" option must be the same for @babel/plugin-proposal-class-properties, @babel/plugin-proposal-private-methods and @babel/plugin-proposal-private-property-in-object (when they are enabled): you can silence this warning by explicitly adding
	["@babel/plugin-proposal-private-methods", { "loose": false }]
to the "plugins" section of your Babel config.
Though the "loose" option was set to "true" in your @babel/preset-env config, it will not be used for @babel/plugin-proposal-private-methods since the "loose" mode option was set to "false" for @babel/plugin-proposal-class-properties.

These should be addressed.

[halocline]

Left a comment on the open PR with my findings: #5419 (comment)