docs: clear the pending release notes for 1.6

The pending release notes were for v1.5, now cleared for adding
v1.6 features.

Signed-off-by: Travis Nielsen <tnielsen@redhat.com>

PendingReleaseNotes.md

@@ -1,6 +1,6 @@
 # Major Themes
 
-v1.5...
+v1.6...
 
 ## K8s Version Support
 
@@ -10,26 +10,8 @@ v1.5...
 
 ### Ceph
 
-- Ceph mons require an odd number for a healthy quorum. An even number of mons is now disallowed.
-- Update deprecated CRD apiextensions.k8s.io/v1beta1 to v1 ([#6424](https://github.com/rook/rook/pull/6424))
-- preservePoolsOnDelete is deprecated for CephFilesystem and is no longer allowed because of data-loss concerns. preserveFilesystemOnDelete acts as a replacement and preserves the filesystem when the CephFilesystem CRD is deleted (which implicitly includes all associated pools). See [#6495](https://github.com/rook/rook/pull/6495) for more details.
-- The discovery daemon is disabled by default since the discovery is not necessary in most clusters. Enable the discovery daemon if
-  devices are being added to nodes and you want to automatically configure OSDs on new devices without restarting the operator.
-- The CRDs have been separated from common.yaml into crds.yaml to give more flexibility for upgrades.
-
 ## Features
 
 ### Core
 
-* Discover Agent: Custom labels can be added to the DaemonSet Pods.
-
 ### Ceph
-
-* Stretch clusters for mons and OSDs to work reliably across two datacenters (Experimental mode)
-* Ceph Block Pool: add mirroring with snapshot scheduling support
-* Ceph Block Pool: add `replicasPerFailureDomain` to set the number of replica in a failure domain ([#5591](https://github.com/rook/rook/issues/5591))
-* Ceph Cluster: export the storage capacity of the ceph cluster ([#6475](https://github.com/rook/rook/pull/6475))
-* Ceph Cluster: add encryption support with Key Management Service
-* The helm chart is updated to v3.4
-  * A `crds.enabled` setting allows the CRDs to be managed separately from the helm chart
-* Ceph CSI: DaemonSet and Deployment Pods can have custom labels added to them