recovery: Do not abort install on detecting older security patch level

Change-Id: If8a3ab7347e51c90337c4044826226ea11d6a327
diff --git a/install/install.cpp b/install/install.cpp
index 5bb23e3..4a7ad2e 100644
--- a/install/install.cpp
+++ b/install/install.cpp
@@ -414,8 +414,7 @@
 
   const auto current_spl = android::base::GetProperty("ro.build.version.security_patch", "");
   if (ViolatesSPLDowngrade(zip, current_spl)) {
-    LOG(ERROR) << "Denying OTA because it's SPL downgrade";
-    return INSTALL_ERROR;
+    LOG(WARNING) << "The OTA package will downgrade security patch level";
   }
 
   if (package_is_ab) {