COMP: remove GDAL_LIBRARY from OTBConfig. it is not used by external project

CMake/OTBConfig.cmake.in

@@ -16,9 +16,6 @@ SET(OTB_USE_EXTERNAL_ITK "@OTB_USE_EXTERNAL_ITK@")
 # Option use external ITK.
 SET(OTB_USE_EXTERNAL_FLTK "@OTB_USE_EXTERNAL_FLTK@")
 
-# GDAL library path
-SET(GDAL_LIBRARY "@GDAL_LIBRARY@")
-
 # The OTB source tree.
 SET(OTB_SOURCE_DIR "@OTB_SOURCE_DIR@")