Fix selection issue with the charts dropdown

[momesgin]

Summary

Fixes #12273

Technical notes summary

As discussed with @codyrancher we probably don't want the emits array at all in vue-select-overrides.js. It does all the emitting on a vue instance that gets passed to the mappedKeys method.

Areas or cases that should be tested

Local -> Apps -> Charts
Click "All" dropdown
Try unselecting any item

Areas which could experience regressions

n/a

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