Revert 2836 - Add AV embed timeout handling to MP

[simonsinclair]

Overall change: This is a manual revert of #2836, which added AV embed timeout handling to Media Player. We had to revert this due to a strange interaction with Simorgh's e2e tests, which could be related to a bug in Cypress. See below for additional context. Until we can offer this issue more time, this functionality will be reverted.

Code changes:

• Revert changes made in Add AV embed timeout handling to Media Player #2836.
• Bump package to 2.6.0.
• Add changelog entry.

Additional context:

• Attaching an on load event handler to Canonical MP iframe causes the first e2e test that accesses the iframe's contentWindow property to fail. Subsequent tests will pass. It does not matter on the order of these tests - the first one will always fail.
• A possible related open issue with Cypress: Handle stale load events that leak from previous windows  cypress-io/cypress#4973.
• When we can afford more time to this problem, it might be worth replicating this issue in a slim repository that mimics our setup and use it to raise a bug report with Cypress.

---

• I have assigned myself to this PR and the corresponding issues
• Automated jest tests added (for new features) or updated (for existing features)
• This PR requires manual testing

[j-pendlebury]

LGTM 👍