[lsan] Sequesters the entire rapidjson package

Apparently it is responsible for a whole slew of leaks such as the one
in the bug below.  It looks like adding public_deps here propagates to
all uses.

I'll re-verify with an integration patch. But if true, this will save us
a lot of time in bug-filing.

Bug: 47266
Change-Id: I67a82ee971abba333a246351c6264c0cf9f828dd
diff --git a/BUILD.gn b/BUILD.gn
index b5c483e..ed48a9c 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -87,4 +87,6 @@
   ]
 
   public_configs = [ ":rapidjson_config" ]
+
+  public_deps = [ "//build/config/sanitizers:suppress-lsan.DO-NOT-USE-THIS" ]
 }