Upload icon is now material design "attachment"
Upload icon is now material design "attachment"

Use attachment icon from material design for file uploads.
Also fixes an alignment issue with nextcloud-vue 4.0.0.

Signed-off-by: Vincent Petry <87e1f221a672a14a323e57bb65eaea19d3ed3804@nextcloud.com>

nextcloud/spreed,nextcloud/spreed,nextcloud/spreed