filter-caption.html.twig shouldn't have a variable named "node"

Problem/Motivation

See: https://api.drupal.org/api/drupal/core%21modules%21filter%21templates%21filter-caption.html.twig/11.x

It doesn't seem like a good idea to name a variable "node" if it's not related to a Drupal node. It is just extremely confusing.

Steps to reproduce

Proposed resolution

Rename this variable to something like "content" (while content is also confusing, as it's the default name of entity render arrays, but even better than "node").

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet