ref(style-spec): remove unused sort-object dep

[AbhiPrasad]

[email protected] isn't used anywhere, so removing it from deps. This eliminates the 23 KB / 18 deps that sort-object brings in when you download @mapbox/mapbox-gl-style-spec.

ref: https://npmgraph.js.org/?q=sort-object

Launch Checklist

• Make sure the PR title is descriptive and preferably reflects the change from the user's perspective.
• Add additional detail and context in the PR description (with screenshots/videos if there are visual changes).
• Manually test the debug page.
• Write tests for all new functionality and make sure the CI checks pass.
• Document any changes to public APIs.
• Post benchmark scores if the change could affect performance.
• Tag @mapbox/map-design-team @mapbox/static-apis if this PR includes style spec API or visual changes.
• Tag @mapbox/gl-native if this PR includes shader changes or needs a native port.

[CLAassistant]

All committers have signed the CLA.

[stepankuzmin]

Looks good to me, thanks!

[AbhiPrasad]

Signed the CLA - thanks for the quick review!