[pkg] Use the new deprecated_system_package alias

PKG-46

Change-Id: I98fa7229b15a53ee1408a7a0499136104d7f3e34
diff --git a/BUILD.gn b/BUILD.gn
index e45ad9d..dace191 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -66,7 +66,7 @@
   # are needed by the library.
   # TODO(aarongreen): Rename this to "root_certs" or suchlike.
   package("libssl") {
-    system_image = true
+    deprecated_system_image = true
     deps = [
       ":ssl",
     ]
@@ -91,7 +91,7 @@
 ##########################
 if (is_fuchsia) {
   package("boringssl_tool") {
-    system_image = true
+    deprecated_system_image = true
     deps = [
       ":bssl",
     ]
@@ -140,7 +140,7 @@
 if (is_fuchsia) {
   package("boringssl_tests") {
     testonly = true
-    system_image = true
+    deprecated_system_image = true
     deps = [
       ":crypto_test",
       ":ssl_test",