channels: Add candidate-4.4, fast-4.4, and stable-4.4

So that Cincinnati doesn't complain when the console bumps its
hard-coded list of channels and starts asking for stable-4.4 ([1] is
in flight to remove the need for the console to hard-code available
channels, but hasn't seen much recent progress).  And even without the
console issue, the installer has been putting new clusters in
stable-4.4 since openshift/installer@d7fb12c07a (bootkube: Update to
stable-4.4 channel, 2020-01-16, openshift/installer#2940).

[1]: openshift/enhancements#123

channels/candidate-4.4.yaml

@@ -0,0 +1,2 @@
+name: candidate-4.4
+versions: []

channels/fast-4.4.yaml

@@ -0,0 +1,2 @@
+name: fast-4.4
+versions: []

channels/stable-4.4.yaml

@@ -0,0 +1,2 @@
+name: stable-4.4
+versions: []