[Bug] g.extension uses wrong path

[micha-silver]

Name of the addon
r.traveltime, but same error for any addon

Describe the bug
Running g.extension r.traveltime errors with:

svn: E170013: Unable to connect to a repository at URL 'https://github.com/OSGeo/grass-addons/branches/grass8/src/raster/r.traveltime'
svn: E160013: '/OSGeo/grass-addons/branches/grass8/src/raster/r.traveltime' path not found

But the actual path should be:
https://github.com/OSGeo/grass-addons/tree/grass8/src/raster/r.traveltime

To Reproduce
Steps to reproduce the behavior:

1. Run

$ g.extension r.gwr
Fetching <r.gwr> from GRASS GIS Addons repository (be patient)...
svn: E170013: Unable to connect to a repository at URL 'https://github.com/OSGeo/grass-addons/branches/grass8/src/raster/r.gwr'
svn: E160013: '/OSGeo/grass-addons/branches/grass8/src/raster/r.gwr' path not found

Expected behavior
Download extensions from the correct github URL.

Screenshots
If applicable, add screenshots to help explain your problem.

System description (please complete the following information):

• GRASS GIS version 8.2, Debian package

   $ g.version
GRASS 8.2.1 (2023)

Additional context
Add any other context about the problem here.

[neteler]

The solution would be a backport of OSGeo/grass#2895 which replaces SVN checkout (no longer supported by GitHub) with git sparse checkout.

[echoix]

If you're able to update to a 8.3 version, it would be fixed right away.

[micha-silver]

@echoix Debian bookworm is still on 8.2. ☹️