Update git submodules

* Update plugins/download-commands from branch 'master'
  - Align on writing "SHA" in "allowTipSHA1InWant"
    
    Even if git-config key names are case-insensitive, align on writing
    "allowTipSHA1InWant" with upper-cased "SHA" as that is how Git upstream
    [1] and Gerrit code [2] do it.
    
    [1] https://git-scm.com/docs/git-config#git-config-uploadpackallowTipSHA1InWant
    [2] https://gerrit.googlesource.com/plugins/download-commands/+/refs/heads/master/src/main/java/com/googlesource/gerrit/plugins/download/command/GitDownloadCommand.java#42
    
    Change-Id: Ie28ceec4703e22d696a3601a0e61ad52ca121b29
    
diff --git a/plugins/download-commands b/plugins/download-commands
index 8357e94..6ee2462 160000
--- a/plugins/download-commands
+++ b/plugins/download-commands
@@ -1 +1 @@
-Subproject commit 8357e942dd9da82884a4e1b6e4697479153d0496
+Subproject commit 6ee246245b9200062e753d1c6943d5782cb7fee0