querystring.unescape does not correctly unescape percent characters

[watilde]

• Version: v12, master
• Platform: Windows, macOS
• Subsystem: querystring

What steps will reproduce the bug?

const querystring = require('querystring');
console.log( 'expected: %*', `actual: ${querystring.unescape('%%2f')}`);
// => actual: %%2f
console.log( 'expected: %2*f*', `actual: ${querystring.unescape('%2%2af%2a')}`);
// => actual %2%2af*

What is the expected behavior?

It should unescape %2a to *.

What do you see instead?