Replace learn staging URL

[OlivierFreyssinet]

Change staging URL used for the Learn page (for a purpose of testing by the e-commerce team).

🦒 Context (issues, jira)

LIVE-1925

💻 Description / Demo (image or video)

🖤 Expectations to reach

PR must pass CI, rebase develop if conflicts. Thanks!

• on QA: at least one of these two checkboxes must be checked:
  • a specific test planned is defined on Jira
  • this PR is covered by automatic UI test
• on delivery: at least one of these two checkboxes must be checked:
  • Option 1: no impact: The changes of this PR have ZERO impact on the userland (invisible for users)
  • Option 2: atomic delivery: the changes is atomic and complete (no partial delivery)

[github-actions]

Thanks for your contribution.
To be able to merge in develop branch, you need to:

• pass the CI
• if needed, run /generate-screenshots
• have a dev review
• have a QA review
• if needed, /upgrade-llc

Why /generate-screenshots ?

If your PR contains UI related changes,
it might be necessary to regenerate screenshots.

Why /upgrade-llc ?

If your PR requires an update to the ledger-live-common library,
once the PR is merged on develop on ledger-live-common side,
you need to run /upgrade-llc to switch back to ledger-live-common@develop here before merging.

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🔴	Statements	8.74%	9/103
🔴	Branches	0%	0/19
🔴	Functions	2.94%	1/34
🔴	Lines	8.33%	8/96

Test suite run success

1 tests passing in 1 suite.

Report generated by 🧪jest coverage report action from 4a32774