Link RDAP syntax page to Github RDAP user's guide

It has been decided that we will link the RDAP help pages, not to local HTML copies, but to the Github documentation.

A typo and word order error in the Github version of the user's guide are also
corrected.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=174350665

java/google/registry/config/RegistryConfig.java

@@ -1104,6 +1104,7 @@ public final class RegistryConfig {
                   "entities?handle=XXXX",
                   "help/XXXX"))
               .setLinkValueSuffix("help/syntax")
+              .setLinkHrefUrlString("https://github.com/google/nomulus/blob/master/docs/rdap.md")
               .build())
           .put("/tos", RdapNoticeDescriptor.builder()
               .setTitle("RDAP Terms of Service")