Bump wagtail from 2.7.2 to 2.11.6 in /v1_13_2/dockerfiles/build/backend#4

dependabot[bot] wants to merge 1 commit intov1.13.2trydirect/wagtail:v1.13.2from

dependabot/pip/v1_13_2/dockerfiles/build/backend/wagtail-2.11.6trydirect/wagtail:dependabot/pip/v1_13_2/dockerfiles/build/backend/wagtail-2.11.6Copy head branch name to clipboard