Yes, you can remove documents from Datashare. But at the moment, it will remove all your documents. You cannot remove only some documents.
Click the pink trash icon on the bottom left of Datashare:
And then click 'Yes':
You can them re-analyze a new corpus.
For advanced users only - if you'd like to do it with the Terminal, here are the instructions:
If you're using Mac:
rm -Rf ~/Library/Datashare/index
If you're using Windows:
rd /s /q "%APPDATA%"\Datashare\index
If you're using Linux:
rm -Rf ~/.local/share/datashare/index