[SCons] Fix minor typo in warning message
[SCons] Fix minor typo in warning message

imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera