BUG: Fix unclosed if() block and duplicate project() in CMakeLists.txt

The if(NOT ITK_SOURCE_DIR) block at line 30 was missing its closing
endif() before the option() and include_directories() calls, causing:

  CMake Error at CMakeLists.txt:30 (if):
    Flow control statements are not properly nested.

Also removed the duplicate project(PerformanceBenchmarking) call
(the full project() declaration with VERSION/DESCRIPTION is at line
16) and fixed the unclosed quote in the option() description string.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hjmjohnson

CMakeLists.txt

@@ -48,12 +48,9 @@ if(NOT ITK_SOURCE_DIR)
     # Set the possible values of build type for cmake-gui
     set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release" "MinSizeRel" "RelWithDebInfo")
   endif()
+endif()
 
-project(PerformanceBenchmarking)
-
-option(ITK_USES_NUMBEROFTHREADS "If ITKv5 uses NumberOfThreads (not NumberOfWorkUnits" OFF)
-
-set(PerformanceBenchmarking_LIBRARIES PerformanceBenchmarking)
+option(ITK_USES_NUMBEROFTHREADS "If ITKv5 uses NumberOfThreads (not NumberOfWorkUnits)" OFF)
 
 include_directories(${CMAKE_BINARY_DIR})
 if(NOT ITK_SOURCE_DIR)