[forms] fix the value of the capture attribute for image upload
[forms] fix the value of the capture attribute for image upload

Refs #1304

3liz/lizmap-web-client,rldhont/lizmap-web-client,rldhont/lizmap-web-client,rldhont/lizmap-web-client,laurentj/lizmap-web-client,rldhont/lizmap-web-client,nboisteault/lizmap-web-client,laurentj/lizmap-web-client,3liz/lizmap-web-client,nboisteault/lizmap-web-client,nboisteault/lizmap-web-client,laurentj/lizmap-web-client,nboisteault/lizmap-web-client,laurentj/lizmap-web-client,3liz/lizmap-web-client,3liz/lizmap-web-client