[monodroid] Remove dead JNI weak-ref checking code (#6074)

Context: https://code.google.com/p/android/issues/detail?id=63929
Context: https://android-review.googlesource.com/c/platform/art/+/73142

ART issue this code worked around was fixed in December 2019 and
released in one of the Android 4.4 (KitKat, API 19) updates, most
likely 4.4.3 on June 2, 2014.

Additionally, the `persist.sys.dalvik.vm.lib` system property doesn't
appear to be present any longer on newer Android versions.

Remove the dead code from `OSBridge::platform_supports_weak_refs()`.

Author: grendello

src/monodroid/jni/osbridge.cc

@@ -1010,33 +1010,7 @@ OSBridge::platform_supports_weak_refs (void)
 			return use_weak_refs;
 	}
 
-	if (androidSystem.monodroid_get_system_property ("persist.sys.dalvik.vm.lib", &value) > 0) {
-		int art = 0;
-		if (!strcmp ("libart.so", value))
-			art = 1;
-		free (value);
-		if (art) {
-			int use_java = 0;
-			if (androidSystem.monodroid_get_system_property ("ro.build.version.release", &value) > 0) {
-				// Android 4.x ART is busted; see https://code.google.com/p/android/issues/detail?id=63929
-				if (value [0] != 0 && value [0] == '4' && value [1] != 0 && value [1] == '.') {
-					use_java = 1;
-				}
-				free (value);
-			}
-			if (use_java) {
-				log_warn (LOG_GC, "JNI weak global refs are broken on Android with the ART runtime.");
-				log_warn (LOG_GC, "Trying to use java.lang.WeakReference instead, but this may fail as well.");
-				log_warn (LOG_GC, "App stability may be compromised.");
-				log_warn (LOG_GC, "See: https://code.google.com/p/android/issues/detail?id=63929");
-				return 0;
-			}
-		}
-	}
-
-	if (api_level > 7)
-		return 1;
-	return 0;
+	return 1;
 }
 
 void