Drop optional dependency

Author: juliolmuller

package.json

@@ -1,6 +1,6 @@
 {
  "name": "file2arraybuffer",
- "version": "1.2.0",
+ "version": "1.2.1",
  "description": "Basic function to convert files into ArrayBuffer objects.",
  "author": "Julio L. Muller",
  "license": "MIT",
@@ -27,9 +27,6 @@
  "build": "rollup --config",
  "lint": "eslint src/ --fix"
  },
- "optionalDependencies": {
- "promise-polyfill": "^8.2.0"
- },
  "devDependencies": {
  "@babel/core": "^7.14.6",
  "@babel/preset-env": "^7.14.7",