Fix browser testing guidance links

[AyobamiH]

Summary

• replace the two inaccessible NHS Architecture browser-guidance links with the public GOV.UK Service Manual guidance
• retain the requirement to choose an appropriate browser matrix and add the Service Manual's analytics-based decision point
• remove the link-check suppression that existed only for the inaccessible links

Why

Issue #358 identifies that the existing Staff and Citizens links no longer provide usable browser guidance. The GOV.UK page supplies a maintained browser and device test matrix and separate advice for public-facing and internal-government services.

Validation

Validated the exact PR head, ce8b205, against base 02563df in GitHub Actions run 33189244956:

• BRANCH_NAME=main scripts/markdown-check-format.sh
• verified a one-commit, one-file diff and ran git diff --check origin/main...HEAD
• confirmed the two inaccessible Aalto links and their link-check suppression are removed
• fetched the GOV.UK page and confirmed it contains the current browser matrix and analytics guidance
• confirmed a clean tracked working tree

The upstream SonarCloud check and SonarCloud Code Analysis both passed for this head. The upstream Check Markdown Format run is currently action_required and has not executed any jobs; it still requires maintainer approval.

Closes #358

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud