DOC: Fix typo in Developer instructions page.
DOC: Fix typo in Developer instructions page.

Fix typo in the "Review changes in a browser" section: change "nstalled"
to "installed".

lorensen/VTKExamples,lorensen/VTKExamples,lorensen/VTKExamples,lorensen/VTKExamples,lorensen/VTKExamples,lorensen/VTKExamples,lorensen/VTKExamples