[Pharo-dev] please test: Make Spec use RubPluggableTextMorph instead of PluggableTextMorph

[stepharo]

https://pharo.fogbugz.com/default.asp?15774
Like that we can get rid of the bug 
https://pharo.fogbugz.com/default.asp?15773
where SHRB is doing wrong semantic analysis and this is one less ref to 
PluggableTextMorph.


We are trying to get rid of it by either using RubPluggableTextMorph or 
and better RubScrolledTextModel

Stef