Remove Array.flatMap polyfill

This has been supported natively since Node v11, Chrome 69, Firefox 62
and Safari 12.

package.json

@@ -43,9 +43,7 @@
     "test-cjs": "yarn build-cjs && nyc mocha -r build-cjs/test/init.js build-cjs/test/*.js",
     "test:compat": "yarn test --preact-compat-lib preact/compat"
   },
-  "dependencies": {
-    "array.prototype.flatmap": "^1.2.1"
-  },
+  "dependencies": {},
   "files": [
     "build/src/**/*",
     "build-cjs/src/**/*",

src/preact10-rst.ts

@@ -10,7 +10,6 @@
 
 import type { NodeType, RSTNode } from 'enzyme';
 import { Component, Fragment, VNode } from 'preact';
-import flatMap from 'array.prototype.flatmap';
 
 import { childElements } from './compat.js';
 import {
@@ -47,7 +46,7 @@ function rstNodesFromChildren(nodes: (VNode | null)[] | null): RSTNodeTypes[] {
   if (!nodes) {
     return [];
   }
-  return flatMap(nodes, (node: VNode | null) => {
+  return nodes.flatMap(node => {
     if (node === null) {
       // The array of rendered children may have `null` entries as a result of
       // eg. conditionally rendered children where the condition was false.

yarn.lock

@@ -451,15 +451,6 @@ array.prototype.flat@^1.2.3:
     define-properties "^1.1.3"
     es-abstract "^1.17.0-next.1"
 
-array.prototype.flatmap@^1.2.1:
-  version "1.2.3"
-  resolved "https://registry.yarnpkg.com/array.prototype.flatmap/-/array.prototype.flatmap-1.2.3.tgz#1c13f84a178566042dd63de4414440db9222e443"
-  integrity sha512-OOEk+lkePcg+ODXIpvuU9PAryCikCJyo7GlDG1upleEpQRx6mzL9puEBkozQ5iAx20KV0l3DbyQwqciJtqe5Pg==
-  dependencies:
-    define-properties "^1.1.3"
-    es-abstract "^1.17.0-next.1"
-    function-bind "^1.1.1"
-
 asn1@~0.2.3:
   version "0.2.4"
   resolved "https://registry.yarnpkg.com/asn1/-/asn1-0.2.4.tgz#8d2475dfab553bb33e77b54e59e880bb8ce23136"