README: rename Python to Python2
Many common GNU/Linux distributions like Ubuntu and Debian does not have python package anymore, so it can not be installed, thus the command fails and OpenWrt 19.07 requires to install Python2 [1]
Fixes:
Package python is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
python2-minimal:i386 python2:i386 python2-minimal python2 dh-python 2to3
python-is-python3
E: Package 'python' has no installation candidate
Reported-by: @mhanak
Edited by Josef Schlehofer