Update notes for submitted changes

* Add jgit-4.17-staging target platform for 2020-09
* Update target platform to R20200831200620

81/2c3969e6564ed7cf62588f5962f1e5d5b98d58

@@ -0,0 +1,7 @@
+Verified+1: JGit Bot <jgit-bot@eclipse.org>
+Code-Review+2: Matthias Sohn <matthias.sohn@sap.com>
+Submitted-by: Matthias Sohn <matthias.sohn@sap.com>
+Submitted-at: Tue, 01 Sep 2020 07:28:59 -0400
+Reviewed-on: https://git.eclipse.org/r/c/jgit/jgit/+/168439
+Project: jgit/jgit
+Branch: refs/heads/stable-5.9

b5/1ed023ff87cda3684481ca38beef568a99f4e9

@@ -0,0 +1,7 @@
+Verified+1: JGit Bot <jgit-bot@eclipse.org>
+Code-Review+2: Matthias Sohn <matthias.sohn@sap.com>
+Submitted-by: Matthias Sohn <matthias.sohn@sap.com>
+Submitted-at: Tue, 01 Sep 2020 07:28:59 -0400
+Reviewed-on: https://git.eclipse.org/r/c/jgit/jgit/+/168440
+Project: jgit/jgit
+Branch: refs/heads/stable-5.9