[Seaside] Correction for 'Installing external projects' in on-click image for pharo

[fritz schenk]

In fourth paragraph:
"- For web application development, we recommend the Seaside project. Seaside is
the heretic web framework that let you build complex web applications in
Smalltalk in a quickly, reusably and maintainably way.
Look at http://www.seaside.st/ and http://book.seaside.st/book for more information.
To install Seaside 3.8, just evaluate:""

You see 'Seaside 3.8' - it should say 3.0.