feat(billing): Update spend notifications documentation (#10076)

* feat(billing): Update spend notifications documentation

* Update docs/product/alerts/notifications/index.mdx

Co-authored-by: Liza Mock <liza.mock@sentry.io>

* Update docs/product/alerts/notifications/index.mdx

Co-authored-by: Liza Mock <liza.mock@sentry.io>

* Update docs/product/alerts/notifications/notification-settings.mdx

Co-authored-by: Liza Mock <liza.mock@sentry.io>

---------

Co-authored-by: Liza Mock <liza.mock@sentry.io>

Author: dashed

docs/product/alerts/notifications/index.mdx

@@ -8,7 +8,7 @@ Sentry sends you notifications regarding workflow activities, [release deploys](
 
 - [Workflow](#workflow-notifications): Activity involving user actions and state changes on issues. This includes activities such as issue resolution, assignment, comments, and regressions.
 - [Deploy](#deploy-notifications): When a release you have commits on is deployed.
-- [Quota](#quota-notifications): Approaching quotas, exceeded quotas, and spike protection.
+- [Spend](#spend-notifications): When you're getting close to spending your reserved volume, your quotas are depleted, and/or your on-demand budget is being put to use.
 - [Weekly Reports](#weekly-reports): A summary of your organization's Sentry activity.
 
 You can manage these notifications in **User Settings > Notifications**.
@@ -47,14 +47,15 @@ Sentry sends deploy notifications to users who have committed to the release tha
 
 ![An example of an email describing deployed features](./img/deploy-emails.png)
 
-## Quota Notifications
+## Spend Notifications
 
-Sentry sends quota notifications to all owners of an organization when:
+By default, Sentry sends spend notifications to all owners of an organization when:
 
-- 80% of the organization's error, transaction, and attachment volume has been depleted.
-- Errors or transactions have exceeded the organization's quota, which includes on-demand capacity
+- 80% of the organization's reserved volume (for errors, transactions, and/or attachments) has been depleted.
+- The entire reserved volume and any on-demand budget for a category (such as errors, transactions, and/or attachments) has been depleted.
+- 80% of the organization's on-demand budget has been used.
 
-You cannot change or disable these notifications. Learn more in the [full Quotas documentation](/pricing/quotas/).
+Learn more in the [full Quotas documentation](/pricing/quotas/).
 
 ## Weekly Reports
 

docs/product/alerts/notifications/notification-settings.mdx

@@ -33,7 +33,7 @@ Here's a list of all the personal notification types you can update:
 - **Issue Workflow:** Changes in issue assignment, resolution status, and comments.
 - **Deploys:** Release, environment, and commit overviews.
 - **Nudges:** Notifications that require review or approval.
-- **Quota:** Error, transaction, and attachment quota limits.
+- **Spend:** Notifications alerting you about your organization's spend and billing quota. 
 - **Weekly Reports:** A summary of the past week for an organization.
 - **Email Routing:** Changes to the email address that receives notifications.
 - **Spike Protection:** Notifications about spikes on a per project basis.