Hosted logos folder contains orphaned svg files

One minor oversight when removing entries from `landscape.yml` is that often the associated svg isn't removed from `./hosted_logos` folder. I did an audit, and there's a few...

```
Starting unused logo check...
Found 1855 unique logo references in './landscape.yml'.
Scanning directory './hosted_logos' for '.svg' files...
Found 2127 '.svg' files in './hosted_logos'.

Result: Found 337 unused '.svg' files:

- ./hosted_logos/1crew.svg
- ./hosted_logos/4intelligence.svg
- ./hosted_logos/99-cloud-kcsp.svg
- ./hosted_logos/99-cloud-ktp.svg
⋮
-----8<------
⋮
- ./hosted_logos/yusur.svg
- ./hosted_logos/zelar.svg
- ./hosted_logos/zte-tecs.svg

Consider removing these files from './hosted_logos' if they are no longer needed.

Script finished successfully.
```

Start with landscape.yml and the hosted_logos directory, using the unused-logo audit output in the issue to identify the orphaned SVG files. Remove only SVGs that are not referenced by landscape.yml, then rerun the audit; done means it reports no unused logo files.

Written by the indexing model from the issue text.