fix: pricing table links to wrong page in docs (p2) (#7434)

## Summary

Continuation of updating pricing table link (p1 was
https://github.com/Comfy-Org/ComfyUI_frontend/pull/7402). Create a
constant since it's now used in multiple locations.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7434-fix-pricing-table-links-to-wrong-page-in-docs-p2-2c86d73d36508199b320d49faa6a0c73)
by [Unito](https://www.unito.io)

src/platform/cloud/subscription/components/SubscriptionPanel.vue

@@ -378,7 +378,7 @@ type TierKey = (typeof TIER_TO_I18N_KEY)[SubscriptionTier]
 
 const DEFAULT_TIER_KEY: TierKey = 'standard'
 
-const { buildDocsUrl } = useExternalLink()
+const { buildDocsUrl, docsPaths } = useExternalLink()
 const authActions = useFirebaseAuthActions()
 const { t } = useI18n()
 
@@ -469,9 +469,7 @@ const {
 
 const handleOpenPartnerNodesInfo = () => {
   window.open(
-    buildDocsUrl('/tutorials/api-nodes/overview#api-nodes', {
-      includeLocale: true
-    }),
+    buildDocsUrl(docsPaths.partnerNodesPricing, { includeLocale: true }),
     '_blank'
   )
 }