Prep release 0.29.1 (#2209)

To pick up recent internal API changes about the crate_info -> dict
changes. Some users like Crubit and rust Protobuf use these internal
APIs, it would be nice for them to be adapted accordingly and refer them
to the new version. But since these are internal, just updating the
minor version.

(it's my first time prepping a release, is there anything beyond just
getting something like this submitted for the released archives to be
created?)

version.bzl

@@ -1,3 +1,3 @@
 """The version of rules_rust."""
 
-VERSION = "0.29.0"
+VERSION = "0.29.1"