wxGUI/extensions: fix reinstall/uninstall multi-addon e.g. wx.metadata

[tmszi]

Describe the bug It is not possible reinstall multi-addon via wxGUI Manage installed GRASS Addons extensions.

To Reproduce Steps to reproduce the behavior:

1. Launch wxGUI
2. Install some multi-addon e.g. g.extension wx.metadata
3. From main window menu choose Settings -> Addons extensions - > Manage installed extension
4. On the Manage installed GRASS Addons extensions window from the list of extensions check checkbox widget for g.gui.metadata addon
5. Hit Reinstall button
6. See error

WARNING: Extension <g.gui.metadata> already installed. Re-installing...
Fetching <g.gui.metadata> from GRASS GIS Addons repository (be patient)...
svn: E170000: URL 'https://github.com/OSGeo/grass-
addons/branches/grass8/src/general/g.gui.metadata' doesn't
exist
ERROR: GRASS Addons <g.gui.metadata> not found

Expected behavior Reinstall multi-addon via wxGUI Manage installed GRASS Addons extensions should be work.

System description (please complete the following information):

• Operating System: all
• GRASS GIS version: all

Additional context The g.extension.all module has an implemented find multi-addon name function.

https://github.com/OSGeo/grass/blob/2dcc9d461848d840655a9bcaed63f86075f06713/scripts/g.extension.all/g.extension.all.py#L163