DOC: improve PreventInSourceBuilds error message

CMake/PreventInSourceBuilds.cmake

@@ -30,7 +30,7 @@ function(AssureOutOfSourceBuilds)
     message("######################################################")
     message("# OTB should not be configured & built in the OTB source directory")
     message("# You must run cmake in a build directory outside of the source tree.")
-    message("# See the documentation for example build commands.")
+    message("# See the software guide documentation for example build commands.")
     message("# ")
     message("# NOTE: Given that you already tried to make an in-source build")
     message("#       CMake has already created several files & directories")