Metadata tweaks

[jamescrake-merani]

Description

Makes some minor improvements to the metadata of the application which is displayed on the Flathub page.

One change affected the the summary line, which has been made shorter so that it fits better onto the page (the old one was too long).

I have labeled this as a draft PR because I am not sure which branch this should be merged in. It might be best to wait until the release branch is merged into main, and then I can rebase this.

How Has This Been Tested?

There are no code changes in this PR.

Review Checklist:

[if using the editor, use [x] in place of [ ] to check a box]

Documentation (check at least one)

• There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)
  • Wheels installer (GH artifact) has been tested (installed and worked)

Licensing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)