Don't include jackson-core in shaded JAR

jackson-core is included in core Gerrit. Use the ":neverlink"
dependency.

Change-Id: I07e13b88b4f5dabebd12dc5542a128c128070339
diff --git a/owners-common/common.bzl b/owners-common/common.bzl
index b752bd6..3c439bc 100644
--- a/owners-common/common.bzl
+++ b/owners-common/common.bzl
@@ -1,5 +1,5 @@
 EXTERNAL_DEPS = [ 
-    '@jackson-core//jar',
+    '@jackson-core//jar:neverlink',
     '@jackson-databind//jar',
     '@jackson-annotations//jar',
     '@jackson-dataformat-yaml//jar',