ConsoleInteraction.py: Change error message
ConsoleInteraction.py: Change error message

This changes error message from
enter a valid letter --> enter a valid letter or number.

Closes https://github.com/coala/coala/issues/5219

jayvdb/coala,coala-analyzer/coala,coala/coala,coala-analyzer/coala,coala-analyzer/coala,coala/coala,jayvdb/coala,SanketDG/coala,SanketDG/coala,jayvdb/coala,SanketDG/coala,coala/coala