Update VRF documentation URL for billing to point to VRF 2.5 page (#2874)

* Update VRF documentation URL for billing to point to VRF 2.5 page

Replaced the existing link that directed users to the VRF V2 documentation with an updated URL pointing to the VRF 2.5 page. This ensures developers access the latest version and features of Chainlink VRF.

Author: bsilagani

src/content/vrf/v2-5/billing.mdx

@@ -71,7 +71,7 @@ Make sure that your consuming contracts have enough funds in either LINK or nati
 <Fragment slot="tab.1">Subscription</Fragment>
 <Fragment slot="tab.2">Direct funding</Fragment>
 <Fragment slot="panel.1">
-You need to pre-fund your subscription enough to meet the [minimum subscription balance](/vrf/v2/subscription#minimum-subscription-balance)
+You need to pre-fund your subscription enough to meet the [minimum subscription balance](/vrf/v2-5/overview/subscription#minimum-subscription-balance)
 in order to have a buffer against gas volatility.
 
 After the request is complete, the final gas cost is recorded based on how much gas is used for the verification and callback.