Don't say composition revisions are beta (#710)

https://github.com/crossplane/crossplane/issues/3715

Revisions became GA in v1.12. I think there's more to do to integrate
them into the main docs flow as a GA feature, but at minimum let's stop
actively saying they're beta.

When the feature became GA, we:

* Made it impossible to disable the feature using the flag.
* Hid the feature flag from the help output.
* Log a warning that the flag will be removed if it is passed.

Signed-off-by: Nic Cope <nicc@rk0n.org>

content/knowledge-base/guides/composition-revisions-example.md

@@ -1,8 +1,5 @@
 ---
 title: Composition Revision Example
-state: beta
-alphaVersion: "1.4"
-betaVersion: "1.11"
 ---
 This tutorial discusses how CompositionRevisions work and how they manage Composite Resource
 (XR) updates. This starts with a `Composition` and `CompositeResourceDefinition` (XRD) that defines a `MyVPC`

content/knowledge-base/guides/composition-revisions.md

@@ -1,8 +1,5 @@
 ---
 title: Composition Revisions
-state: beta
-alphaVersion: "1.4"
-betaVersion: "1.11"
 ---
 
 This guide discusses the use of "Composition Revisions" to safely make and roll

content/master/software/install.md

@@ -244,7 +244,6 @@ at the table below.
 {{< table caption="Feature flags" >}}
 | Status | Flag | Description |
 | --- | --- | --- |
-| Beta | `--enable-composition-revisions` | Enable support for CompositionRevisions. |
 | Beta | `--enable-composition-webhook-schema-validation` | Enable Composition validation using schemas. |
 | Alpha | `--enable-composition-functions` | Enable support for Composition Functions. |
 | Alpha | `--enable-environment-configs` | Enable support for EnvironmentConfigs. |