Ensure proper SSL CAs are available on guix shell

Otherwise, time-machine may fail to pull the channels properly.

Author: jchristgit

guix/README.md

@@ -52,5 +52,5 @@ guix deploy deployment.scm
 # and wish to use the pinned versions (as you should):
 guix time-machine -C channels-lock.scm -- deploy deployment.scm
 # If you wish to sandbox the whole thing in a container:
-guix shell --preserve=^SSH_AUTH_SOCK --expose=/etc/guix --expose=$HOME/.ssh --share=$SSH_AUTH_SOCK --container --network --nesting guix -- guix time-machine -C channels-lock.scm -- deploy deployment.scm
+guix shell --preserve=^SSH_AUTH_SOCK --expose=/etc/guix --expose=$HOME/.ssh --share=$SSH_AUTH_SOCK --container --network --nesting guix nss-certs -- guix time-machine -C channels-lock.scm -- deploy deployment.scm
 ```