Revert "add com.android.threadnetwork to base_system.mk"

This reverts commit 286e55ad94.

Reason for revert: the com.android.threadnetwork module is merged to com.android.tethering module

Bug: 296211911
Change-Id: Id601ab8b6f160d8fc2b7a9720652842cc2c194ba

target/product/base_system.mk

@@ -70,7 +70,6 @@ PRODUCT_PACKAGES += \
     com.android.scheduling \
     com.android.sdkext \
     com.android.tethering \
-    com.android.threadnetwork \
     com.android.tzdata \
     com.android.uwb \
     com.android.virt \