health: make libhealth_aidl_impl visibility public

It was meant to be the replacement of health2impl, the helper library
for implementing the health HAL. Hence, vendor implementation needs
to access it.

Test: pass
Bug: 177269435
Change-Id: I58f4bcd860983b2b16ea52fbdd6e05c8d4953454
diff --git a/health/aidl/default/Android.bp b/health/aidl/default/Android.bp
index c27de7a..a13c677 100644
--- a/health/aidl/default/Android.bp
+++ b/health/aidl/default/Android.bp
@@ -111,10 +111,6 @@
         "Health.cpp",
         "LinkedCallback.cpp",
     ],
-    visibility: [
-        ":__subpackages__",
-        "//hardware/interfaces/tests/extension/health:__subpackages__",
-    ],
     target: {
         recovery: {
             exclude_srcs: [