Remove lmk.log_stats sysprop from mainline_system

It is now set on the /product partition by relevant devices.

Bug: 135569569
Test: lunch mainline_system_arm64; inspect system/etc/prop.default
Change-Id: I34696977f584a65741c6002e6688d86e66a1f121
diff --git a/target/product/mainline_system.mk b/target/product/mainline_system.mk
index 87393d4..f836bd3 100644
--- a/target/product/mainline_system.mk
+++ b/target/product/mainline_system.mk
@@ -99,8 +99,6 @@
 
 # Enable stats logging in LMKD
 TARGET_LMKD_STATS_LOG := true
-PRODUCT_SYSTEM_DEFAULT_PROPERTIES += \
-    ro.lmk.log_stats=true
 
 # Enable dynamic partition size
 PRODUCT_USE_DYNAMIC_PARTITION_SIZE := true