Binding a property or attribute multiple times results in the previous values being overwritten, thus making them useless.
This rule disallows binding the same property multiple times in templates.
The following patterns are considered warnings:
html`<x-foo bar bar>`;
html`<x-foo bar=${x} bar=${y} baz>`;
The following patterns are not warnings:
html`<x-foo bar baz=${x}>`;
If you don't care about repeated bindings, then you will not need this rule.