Update cargo submodule

I'm not really sure what we want the cadence here to be. We'll at the very least
update the Cargo submodule right before all releases, but otherwise I figured we
could just do it whenever needed or otherwise weekly (or something like that).

In any case, I don't have a super strong particular reason to do this, it's just
been a week or so since the release!

diff --git a/cargo b/cargo
index c995e9eb5acf3976ae8674a0dc6d9e958053d9fd..4e95c6b41eca3388f54dd5f7787366ad2df637b5 160000 (submodule)
--- a/cargo
+++ b/cargo
@@ -1 +1 @@
-Subproject commit c995e9eb5acf3976ae8674a0dc6d9e958053d9fd
+Subproject commit 4e95c6b41eca3388f54dd5f7787366ad2df637b5