Replace insert_editor_js hook example with a non-registerHalloPlugin one
Replace insert_editor_js hook example with a non-registerHalloPlugin one

Fixes #3839

zerolab/wagtail,nealtodd/wagtail,gasman/wagtail,rsalmaso/wagtail,rsalmaso/wagtail,FlipperPA/wagtail,wagtail/wagtail,nealtodd/wagtail,kaedroho/wagtail,thenewguy/wagtail,thenewguy/wagtail,zerolab/wagtail,torchbox/wagtail,takeflight/wagtail,jnns/wagtail,thenewguy/wagtail,kaedroho/wagtail,nealtodd/wagtail,timorieber/wagtail,thenewguy/wagtail,gasman/wagtail,mixxorz/wagtail,zerolab/wagtail,timorieber/wagtail,FlipperPA/wagtail,torchbox/wagtail,wagtail/wagtail,thenewguy/wagtail,mikedingjan/wagtail,kaedroho/wagtail,nimasmi/wagtail,mixxorz/wagtail,zerolab/wagtail,mixxorz/wagtail,nimasmi/wagtail,jnns/wagtail,kaedroho/wagtail,rsalmaso/wagtail,torchbox/wagtail,zerolab/wagtail,gasman/wagtail,wagtail/wagtail,gasman/wagtail,takeflight/wagtail,FlipperPA/wagtail,nimasmi/wagtail,rsalmaso/wagtail,takeflight/wagtail,mikedingjan/wagtail,gasman/wagtail,mixxorz/wagtail,timorieber/wagtail,nealtodd/wagtail,rsalmaso/wagtail,takeflight/wagtail,mikedingjan/wagtail,jnns/wagtail,mikedingjan/wagtail,wagtail/wagtail,jnns/wagtail,FlipperPA/wagtail,timorieber/wagtail,nimasmi/wagtail,torchbox/wagtail,mixxorz/wagtail,wagtail/wagtail,kaedroho/wagtail