#319 Taggable input error state

Super simple fix that removes the `box-shadow` from the `:focus` state from the select2 hidden text input within the tag field.

To replicate:

1. Add dataset with a tag with invalid characters. E.g. `test:test`
2. Watch as when you focus into on the tag `input` it shows a odd red halo on master... and not in this changeset

Good times.