COMP: ExtractSkeleton - Fix clang -Wparentheses-equality warning

Detailed output from Clang:

 warning: equality comparison with extraneous parentheses [-Wparentheses-equality]
        if( (result[i] == OBJ) )
             ~~~~~~~~~~^~~~~~
 note: remove extraneous parentheses around the comparison to silence this warning

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22037 3bd1e089-480b-0410-8dfb-8563597acbee