Fixes a11y warning in 06-select-bindings tutorial

[gsimone]

The Select Bindings examples shows an accessibility warning:

A11y: on:blur must be used instead of on:change, unless absolutely necessary and it causes no negative consequences for keyboard only or screen reader users. (24:1)

[Conduitry]

I think we probably want to figure out what to do with #4946 before doing something like this. Changing from on:change to on:blur results in different behavior, and I think we should first decide what we want the warning to be exactly, and when it should appear.

[gsimone]

I agree, although using on:blur doesn't really make a difference in the context of the example, it's just something that - looks - like a user error.