Remove the a11y_title field when updating H5PContent

Problem/Motivation

When disabling revisions for the node bundle to which the h5p field is attached, h5p attempts to update the H5PContent instead of cloning a new one. The update fails since it tries to update the a11y_title field, which doesn't exist on the H5PContent entity. Without the attached patch it isn't possible to update H5PContent.

Steps to reproduce

Disable revisioning for the node entity and try to update the h5p on the field of that node. It will fail with an exception.

Proposed resolution

Remove the a11y_title field from the h5p metadata.

Remaining tasks

Review and apply the attached patch.

User interface changes

API changes

Data model changes