43812: Exercise - Work instruction - Card title Schedule needs a heading markup

[GitHamo]

This PR addresses accessibility issue 0043812: in the Exercise module, under Work Instruction, the card title "Schedule" lacked proper heading markup.

Added an h4 heading to the card title, ensuring it appears as a subordinate to the main "Work Instruction" heading.

https://mantis.ilias.de/view.php?id=43812

[GitHamo]

~~Open~~

~~Since this is a kitchen sink element, which means it might affect other parts of the ILIAS dashboard as well, should the expected test results in the following files also be updated, or at least the one related to the Card component?~~

• components/ILIAS/UI/tests/Component/Card/CardTest.php (3 occurrences)
• components/ILIAS/UI/tests/Component/Card/RepositoryObjectTest.php (4 occurrences)
• components/ILIAS/UI/tests/Component/Deck/DeckTest.php (7 occurrences)
• components/ILIAS/UI/tests/Component/Panel/PanelTest.php (2 occurrences) ~~

EDIT: Added the changes to tests as well. Now it passes ✅