Rename PRODUCT_UPDATABLE_SYSTEM_SERVER_JARS to PRODUCT_APEX_SYSTEM_SERVER_JARS.

Regardless of an "updatable" property, list all apex jars in the same
variable. This is less confusing for devs and matches the pattern with
PRODUCT_APEX_BOOT_JARS.

Bug: 191127295
Test: atest CtsClasspathsTestCases
Change-Id: I3b12f26237636f4271cb000480928b3ce1c2e62f
Merged-In: I3b12f26237636f4271cb000480928b3ce1c2e62f
diff --git a/core/product.mk b/core/product.mk
index a87e287..f6347e8 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -234,7 +234,7 @@
 _product_list_vars += PRODUCT_SYSTEM_SERVER_APPS
 _product_list_vars += PRODUCT_SYSTEM_SERVER_JARS
 # List of system_server jars delivered via apex. Format = <apex name>:<jar name>.
-_product_list_vars += PRODUCT_UPDATABLE_SYSTEM_SERVER_JARS
+_product_list_vars += PRODUCT_APEX_SYSTEM_SERVER_JARS
 # If true, then suboptimal order of system server jars does not cause an error.
 _product_single_value_vars += PRODUCT_BROKEN_SUBOPTIMAL_ORDER_OF_SYSTEM_SERVER_JARS