simplify upload icon

core/img/actions/upload.svg

+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <svg xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://www.w3.org/2000/svg" height="16" width="16" version="1.1" xmlns:cc="http://creativecommons.org/ns#" xmlns:dc="http://purl.org/dc/elements/1.1/">
- <path d="M10,12,6,12,6,6,2,6,8,0,14,6,10,6z"/>
- <path fill="#000" d="m0,11,0,5,16,0,0-5-2,0,0,3-12,0,0-3z"/>
+ <path d="m8 1-6 6h4v4h4v-4h4zm-6 12v2h12v-2z"/>
 </svg>