gh-571: add a 20 min timeout to example runs

[Saransh-cpp]

Description

The examples roughly take 12-13 minutes to run. A 20 minutes timeout on this particular step should be good!

Closes: #571

Checks

• Is your code passing linting?
• Is your code passing tests?
• Have you added additional tests (if required)?
• Have you modified/extended the documentation (if required)?
• Have you added a one-liner changelog entry above (if required)?

[paddyroddy]

We might need to change this once #535 is merged, but let's see