Remove SCAL link

[jakecosgrove]

Description

This PR fixes some minor errors to some links, including:

• In /campaigns /event-based-messaging and /direct-messaging the 'Find out how to pay' link in Message performance and charging takes you to the wrong destination
• the link to the Supplier Conformance Assessment List (SCAL) takes you to NHS Login's SCAL rather than a generic definition of a SCAL

The link destinations have been corrected or removed where applicable.

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming

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Sensitive Information Declaration

To ensure the utmost confidentiality and protect your and others privacy, we kindly ask you to NOT including PII (Personal Identifiable Information) / PID (Personal Identifiable Data) or any other sensitive data in this PR (Pull Request) and the codebase changes. We will remove any PR that do contain any sensitive information. We really appreciate your cooperation in this matter.

• I confirm that neither PII/PID nor sensitive data are included in this PR and the codebase changes.

[emmagifford]

All looks good! The 3 links in the use case pages are all fixed and the SCAL reference in /onboard-with-nhs-notify no longer links to the incorrect page.