docs: get rid of empty custom scopes placeholder (#10423)

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# Which Problems Are Solved

<img width="1402" height="807" alt="image"
src="https://github.com/user-attachments/assets/9c931889-600f-475c-8a8e-eff592d9acae"
/>

# How the Problems Are Solved

Removing the Custom Scopes Placeholder.

Co-authored-by: Rajat Singh <rajat@zitadel.com>
Co-authored-by: Livio Spring <livio.a@gmail.com>

docs/docs/apis/openidoauth/scopes.md

@@ -16,10 +16,6 @@ ZITADEL supports the usage of scopes as way of requesting information from the I
 | phone          | Optional scope to request the phone of the subject                             |
 | offline_access | Optional scope to request a refresh_token (only possible when using code flow) |
 
-## Custom Scopes
-
-> This feature is not yet released
-
 ## Reserved Scopes
 
 In addition to the standard compliant scopes we utilize the following scopes.