fix(http): Use HTTP 1.1 for upstreams (#369)

diff --git a/conf.d/managed_endpoints.conf b/conf.d/managed_endpoints.conf
index 71336f0..cf601ba 100644
--- a/conf.d/managed_endpoints.conf
+++ b/conf.d/managed_endpoints.conf
@@ -82,6 +82,7 @@
             routing.processCall(ds.init())
         }
 
+        proxy_http_version 1.1;
         proxy_pass $upstream;
         header_filter_by_lua_block {
             local cors = require "cors"