Docs: PO only allowed on annual Pro/Enterprise plans (#11335)

* Docs: PO only allowed on annual Pro/Enterprise plans

Small refactor of our docs explaining PO support.

* Update docs/user/commercial/subscriptions.rst

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Co-authored-by: Eric Holscher <[email protected]>

Author: humitos

docs/user/commercial/subscriptions.rst

@@ -42,8 +42,8 @@ Billing information
 
 We provide both monthly and annual subscriptions for all plans.
 Annual plans are given a 2 month discount compared to monthly billing.
-We only support credit card billing for our Basic and Advanced plans.
-For our Pro and Enterprise users, we support invoice-based and PO billing.
+We support credit card billing for all plans.
+Pro and Enterprise plans can use invoice-based and PO billing for annual subscriptions.
 
 .. tip::
     We recommend paying by credit card for all users,