Remove fast_unwind_on_malloc and malloc_context_size restrictions in ASAN CI (#42515)

No need to set ASAN_OPTIONS any more either: these options are already
set in `loader_exe.c` with `__asan_default_options`.

Author: tkf

contrib/asan/Make.user.asan

@@ -18,6 +18,3 @@ override WITH_GC_DEBUG_ENV=1
 
 # default to a debug build for better line number reporting
 override JULIA_BUILD_MODE=debug
-
-# make ASAN consume less memory
-export ASAN_OPTIONS=detect_leaks=0:fast_unwind_on_malloc=0:allow_user_segv_handler=1:malloc_context_size=2