fix typo in babel-preset-env

[gera2ld]

Q	A
Fixed Issues?
Patch: Bug Fix?	Yes
Major: Breaking Change?	No
Minor: New Feature?	No
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?	No
License	MIT

In babel-preset-env, String#italics is incorrectly defined as String#italic for core-js@3.

With a browserslist of defaults, we got the following results:

Case 1: not work because italics is not polyfilled.

// input
console.log('text'.italics());

// output
console.log('text'.italics());

Case 2: still not work because italic is not a function, and the polyfill is useless.

// input
console.log('text'.italic());

// output
import "core-js/modules/es.string.italics";
console.log('text'.italic());

[nicolo-ribaudo]

Thanks!