Add comment to explain why try-with-resource is not used

Change-Id: I904f9890428334bdf2971511e0b2681f3da5a82a

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java

diff --git a/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java b/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java
index 2759b8a..77ed09c 100644
--- a/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java
+++ b/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/UploadPackServlet.java
@@ -169,6 +169,7 @@ public void doPost(HttpServletRequest req, HttpServletResponse rsp)
 
 		UploadPackRunnable r = () -> {
 			UploadPack up = (UploadPack) req.getAttribute(ATTRIBUTE_HANDLER);
+			// to be explicitly closed by caller
 			@SuppressWarnings("resource")
 			SmartOutputStream out = new SmartOutputStream(req, rsp, false) {
 				@Override