manifest: move to Fedora 34

Fedora 34 Beta is GO for March 23:
https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/H6CDDLGK7KWEFGYB2PWOVSUXTYWIH2MA/

As per coreos/fedora-coreos-tracker#704, we
want to move `next` over to it in the next release. So let's move over
`next-devel` now.

manifest-lock.overrides.yaml

@@ -1,30 +1 @@
-packages:
-  # Keep this until we move to Fedora 34.
-  # https://github.com/coreos/fedora-coreos-tracker/issues/649
-  # https://bugzilla.redhat.com/show_bug.cgi?id=1892235#c25
-  systemd:
-    evr: 246.7-1.fc33
-  systemd-container:
-    evr: 246.7-1.fc33
-  systemd-libs:
-    evr: 246.7-1.fc33
-  systemd-pam:
-    evr: 246.7-1.fc33
-  systemd-rpm-macros:
-    evra: 246.7-1.fc33.noarch
-  systemd-udev:
-    evr: 246.7-1.fc33
-  # There's a regression in 5.10.20+ which breaks rootless podman
-  # https://github.com/containers/buildah/issues/3071
-  kernel:
-    evr: 5.10.19-200.fc33
-  kernel-core:
-    evr: 5.10.19-200.fc33
-  kernel-modules:
-    evr: 5.10.19-200.fc33
-  # Fast-track coreos-installer release
-  # https://bodhi.fedoraproject.org/updates/FEDORA-2021-7a0ce6189e
-  coreos-installer:
-    evr: 0.8.0-1.fc33
-  coreos-installer-bootinfra:
-    evr: 0.8.0-1.fc33
+packages: {}