Bazel: Bump java docs api to 11

This is fixing build api breakage with newer Java versions:

javadoc: error - The code being documented uses modules but the \
packages defined in https://docs.oracle.com/javase/8/docs/api/
are in the unnamed module.

Change-Id: Ic3e9f3d24df59b2379d83af02ce1418163204429
diff --git a/tools/javadoc.bzl b/tools/javadoc.bzl
index c7a7e1d..4799254 100644
--- a/tools/javadoc.bzl
+++ b/tools/javadoc.bzl
@@ -25,7 +25,7 @@
     transitive_jar_paths = [j.path for j in transitive_jars.to_list()]
     dir = ctx.outputs.zip.path + ".dir"
     source = ctx.outputs.zip.path + ".source"
-    external_docs = ["https://docs.oracle.com/javase/8/docs/api"] + ctx.attr.external_docs
+    external_docs = ["https://docs.oracle.com/en/java/javase/11/docs/api"] + ctx.attr.external_docs
     cmd = [
         "rm -rf %s" % source,
         "mkdir %s" % source,