Remove webview from media_system.mk

It is present in media_vendor.mk (and soon media_product.mk),
which is the correct place.

Test: make
Change-Id: I7ffda211cf4b01a22ec01c661959defcf59bbc4b
diff --git a/target/product/media_system.mk b/target/product/media_system.mk
index 992e2ed..7d401dc 100644
--- a/target/product/media_system.mk
+++ b/target/product/media_system.mk
@@ -59,7 +59,6 @@
     requestsync \
     StatementService \
     vndk_snapshot_package \
-    webview \
 
 
 PRODUCT_COPY_FILES += \