health: remove unused flag HEALTHD_USE_HEALTH_2_0

Test: boots
Bug: 79107699
Change-Id: Idc27ad452b799ef2ce4f18c787f2aa2afd1dd8cf
(cherry picked from commit 1ffc50ad70dea0d1964bd860a2a40bf8fd2682fc)
diff --git a/health/2.0/default/Android.bp b/health/2.0/default/Android.bp
index 8eb02e0..03aa77b 100644
--- a/health/2.0/default/Android.bp
+++ b/health/2.0/default/Android.bp
@@ -6,8 +6,6 @@
         "healthd_common.cpp",
     ],
 
-    cflags: ["-DHEALTHD_USE_HEALTH_2_0"],
-
     export_include_dirs: ["include"],
 
     shared_libs: [