Upgrade arcconfig to use https

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@275750 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/.arcconfig b/.arcconfig
index 6d07e82..c96fbc1 100644
--- a/.arcconfig
+++ b/.arcconfig
@@ -1,4 +1,4 @@
 {
   "project_id" : "libcxx",
-  "conduit_uri" : "http://reviews.llvm.org/"
+  "conduit_uri" : "https://reviews.llvm.org/"
 }