Update missing image descriptions identified during front end audit

[StephDriver]

Non-text content should have a text alternative. The following images did not have appropriate alt-text when reviewed during #4194. They need to be updated.

• Sample 1, item 24. "Janeway logo final" is read as the title of the logo at hte bottom. The 'final' is unhelpful. <title>Janeway-Logo-Final</title>
• Sample 3, item 12. image description is article title which not only doesn't describe the actual image, but the title then follows as a heading - consider a 'describedby' reference to the heading instead.
• Sample 3, item 51. OLH logo does not have alt-text
• Sample 4, item 20. figure 1 - voiceover attempts to read the text within the png. but as the order is about the visual layout, this makes no sense.
• Sample 4, item 42. press logo at bottom of the page is missing an alt-text so the image file title is read out - this is a collection of numbers and letters. This is due to a missing closing " following the class attribute, which prevents the alt="" attribute being recognised <img src="/media/cover_images/d78e50a8-3542-4429-b049-20261739ee56.svg" class=" alt=" "="">.
• Sample 5.1, item 3. should cover image be set to decorative? Is "[Journal name] cover image" as a description helpful in this context/position on the page?
• Sample 5.2, item 5. latest news image is not described.