Update docs (CrunchyData#3604)

Issue: [sc-18286]

Author: benjaminjb

config/crd/bases/postgres-operator.crunchydata.com_postgresclusters.yaml

@@ -9458,8 +9458,8 @@ spec:
  type: object
  tablespaceVolumes:
  description: The list of tablespaces volumes to mount for this
- postgrescluster This function is currently in alpha as of
- PGO v5.4
+ postgrescluster This field requires enabling TablespaceVolumes
+ feature gate
  items:
  properties:
  dataVolumeClaimSpec:

docs/content/guides/tablespaces.md

@@ -6,8 +6,8 @@ weight: 160
 ---
 
 {{% notice warning %}}
-PGO tablespaces is currently in `Alpha` and may interfere with other features.
-(See below for more details.)
+PGO tablespaces currently requires enabling the `TablespaceVolumes` feature gate
+and may interfere with other features. (See below for more details.)
 {{% /notice %}}
 
 A [Tablespace](https://www.postgresql.org/docs/current/manage-ag-tablespaces.html)
@@ -43,7 +43,7 @@ Postgres Operator adds many conveniences to make it easier to use tablespaces.
 
 ## Enabling TablespaceVolumes in PGO v5
 
-In PGO v5, tablespace support is currently in `Alpha`. If you want to use this
+In PGO v5, tablespace support is currently feature-gated. If you want to use this
 experimental feature, you will need to enable the feature via the PGO `TablespaceVolumes`
 [feature gate](https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/).
 

docs/content/references/crd.md

@@ -204,7 +204,7 @@ PGO allows you to configure custom
 [sidecar Containers](https://kubernetes.io/docs/concepts/workloads/pods/#how-pods-manage-multiple-containers)
 for your PostgreSQL instance and pgBouncer Pods.
 
-To use the custom sidecar features, currently in `Alpha`, you will need to enable
+To use the custom sidecar features, you will need to enable
 them via the PGO
 [feature gate](https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/).
 
@@ -318,7 +318,7 @@ respective Pods until the feature gate is enabled.
 ### Considerations
 
 - Volume mounts and other Pod details are subject to change between releases.
-- The custom sidecar features are currently in `Alpha`. Any sidecar Containers,
+- The custom sidecar features are currently feature-gated. Any sidecar Containers,
  as well as any settings included in their configuration, are added and used at
  your own risk. Improperly configured sidecar Containers could impact the health
  and/or security of your PostgreSQL cluster!

docs/content/tutorial/customize-cluster.md

@@ -480,7 +480,7 @@ type PostgresInstanceSetSpec struct {
 WALVolumeClaimSpec *corev1.PersistentVolumeClaimSpec `json:"walVolumeClaimSpec,omitempty"`
 
 // The list of tablespaces volumes to mount for this postgrescluster
-// This function is currently in alpha as of PGO v5.4
+// This field requires enabling TablespaceVolumes feature gate
 // +listType=map
 // +listMapKey=name
 // +optional