Bump back the Cargo date

alexcrichton · alexcrichton · commit 9333c420da0d · 2016-07-06T09:31:43.000-07:00
This was moved forward by accident
diff --git a/src/stage0.txt b/src/stage0.txt
@@ -14,4 +14,4 @@
 
 rustc: 1.10.0-2016-07-05
 rustc_key: e8edd0fd
-cargo: nightly-2016-07-05
+cargo: nightly-2016-05-22
