I'm not sure you can remove Python 2 altogether, but you can install Python 3 and evoke it specifically instead of Python 2.
First, make sure Python 3 is Installed: Log into your Synology via the web administration and in the 'Package Center' make sure 'Python 3' is installed. (You will find it under 'Developer Tools' within the 'Package Center')
Next, specifically evoke Python 3 by simply calling
You could also try using the locate command on your Synology to find the exact location of Python 2. To do this enter the following on your Synology:
ipkg update ipkg install mlocate
And here is a tutorial on how to use the command: http://www.thegeekstuff.com/2012/03/locate-command-examples/
Also, If you don't have luck on Stack Overflow I'd run over to the Synology Forums for help as well: https://forum.synology.com