Remove LegacyComplex.h (pytorch#39834)

Summary:
All std::complex has been migrated to c10::complex
Pull Request resolved: pytorch#39834

Differential Revision: D22001969

Pulled By: ezyang

fbshipit-source-id: 665a9198afde45a95309053b2f2381e123bf869a

Author: zasdfgbnm

aten/src/ATen/NumericUtils.h

@@ -8,7 +8,6 @@
 #include <complex>
 #include <type_traits>
 #include <c10/util/BFloat16.h>
-#include <c10/util/LegacyComplex.h>
 #include <c10/util/Half.h>
 #include <c10/macros/Macros.h>
 

aten/src/ATen/test/CMakeLists.txt

@@ -36,7 +36,6 @@ list(APPEND ATen_CPU_TEST_SRCS
   ${CMAKE_CURRENT_SOURCE_DIR}/memory_format_test.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/cpu_rng_test.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/ivalue_test.cpp
-  ${CMAKE_CURRENT_SOURCE_DIR}/complex_test.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/vmap_test.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/type_test.cpp)
 

aten/src/ATen/test/complex_test.cpp

@@ -10,7 +10,6 @@ VALGRIND=${VALGRIND:=ON}
 ./atest
 ./scalar_test
 ./broadcast_test
-./complex_test
 ./wrapdim_test
 ./apply_utils_test
 ./dlconvertor_test