Add a beta mark for Perforce permissions feature (#962)

Labels perfore permissions as a beta feature. 

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Author: mmanela

docs/admin/repo/perforce.mdx

@@ -75,7 +75,7 @@ Perforce label names are also more flexible than git tag names, so incompatible
 
 This behaviour can be disabled by setting `noConvertLabels` to `true` in the [fusion client configuration](https://sourcegraph.com/github.com/sourcegraph/sourcegraph@44e848d4ba5a3d47bc6e8651638cfe2279d02102/-/blob/schema/perforce.schema.json?L66-131).
 
-## Repository permissions
+## Repository permissions (Beta)
 
 To enforce file-level permissions for Perforce depots using the [Perforce protects file](https://www.perforce.com/manuals/cmdref/Content/CmdRef/p4_protect.html), include [the `authorization` field](https://sourcegraph.com/github.com/sourcegraph/sourcegraph@2a716bd70c294acf1b3679b790834c4dea9ea956/-/blob/schema/perforce.schema.json?L67-78) in the configuration of the Perforce code host connection you created [above](#add-a-perforce-code-host):