🗑️ Remove WebDAV sync support; SuperSync only 🗑️

WebDAV was added as an alternative sync provider but the design decision
is to ship SuperSync only. Removes all WebDAV env vars, the nginx reverse
proxy block for /webdav/, and the WebDAV branch in __pre_execute that
wrote sync-config-default-override.json. SuperSync behavior is unchanged.
- Dockerfile: drop WEBDAV_BACKEND, WEBDAV_BASE_URL, WEBDAV_USERNAME,
WEBDAV_SYNC_FOLDER_PATH from ENV declarations
- rootfs/usr/local/etc/docker/init.d/zz-nginx.sh: remove WEBDAV_*
variable declarations, nginx /webdav/ proxy location block, and
WebDAV branch in __pre_execute sync config generation

Dockerfile
rootfs/usr/local/etc/docker/functions/entrypoint.sh
rootfs/usr/local/etc/docker/init.d/zz-nginx.sh

rootfs/usr/local/etc/docker/functions/entrypoint.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # shellcheck shell=bash
 # - - - - - - - - - - - - - - - - - - - - - - - - -
-##@Version           :  202606261200-git
+##@Version           :  202606261430-git
 # @@Author           :  Jason Hempstead
 # @@Contact          :  git-admin@casjaysdev.pro
 # @@License          :  LICENSE.md
@@ -802,7 +802,7 @@ __set_user_group_id() {
     return 0
   fi
   if [ -z "$set_user" ] || [ "$set_user" = "root" ]; then
-    return
+    return 0
   fi
   if grep -shq "^$set_user:" "/etc/passwd" "/etc/group"; then
     if __check_for_guid "$set_gid"; then