07-frag-1 : Typo fix - Fixes Issue #64

Small thing...   So that Issue #64 can be closed (matrix change for 06-intro-6 already dealt with).

Martin
:-)

PS:  Even though I'm now a member of `stackgl` I don't seem to have Issue close permissions?  Is there something that I have to do at my end, or is there a permissions system for the organisation's admin?