Add note to Manual Testing instructions about missing wavelength tooltips

[cailafinn]

Description of work

Summary of work

Add a note to the manual testing instructions about missing tooltips for wavelength in the ISIS SANS GUI.

This is a known issue, but low priority for the SANS group right now.

Fixes #35085

Further detail of work

• Added a note to not raise an issue during manual testing if the missing tooltips are found.

To test:

1. Build the dev-docs-html target
2. Check the docs are formatted correctly when opened in a browser.

This does not require release notes because **it is part of the developer documentation only. **

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Reviewer

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[GuiMacielPereira]

Built dev-docs-html and confirmed the changes were added successfully