removeAttribute makes boolean attributes render incorrectly.

[allain]

It appears that removing an attribute causes boolean attributes to be rendered incorrectly:

const {parse} = require("node-html-parser")
const inputEl = parse('<input>').firstChild

inputEl.setAttribute('checked', '')
inputEl.setAttribute('a', '')
console.log(inputEl.toString()) // => <input checked a> CORRECT

inputEl.removeAttribute('a')
console.log(inputEl.toString()) // => <input checked=""> INCORRECT

If it helps narrow it down, the bug does not happen if the boolean attribute was not added using setAttribute:

const {parse} = require("node-html-parser")
const inputEl = parse('<input checked>').firstChild

inputEl.setAttribute('a', '')
console.log(inputEl.toString()) // => <input checked a> CORRECT

inputEl.removeAttribute('a')
console.log(inputEl.toString()) // => <input checked> CORRECT