Update formatting re: marketing emails

Fix the formatting - because part of what was on the page was
incorrectly styled - and cross-link between the API and the page
describing the UI feature.

doc/user/profile/notifications.md

@@ -50,16 +50,16 @@ These notification settings apply only to you. They do not affect the notificati
 
 ## Global notification settings
 
-Your **Global notification settings** are the default settings unless you select different values for a project or a group.
+Your **Global notification settings** are the default settings unless you select
+different values for a project or a group.
 
-- Notification email
-  - This is the email address your notifications are sent to.
-- Global notification level
-  - This is the default [notification level](#notification-levels) which applies to all your notifications.
-- Receive product marketing emails
-  - Check this checkbox if you want to receive periodic emails related to GitLab features.
-- Receive notifications about your own activity.
-  - Check this checkbox if you want to receive notification about your own activity. Default: Not checked.
+- **Notification email**: The email address your notifications are sent to.
+- **Global notification level**: The default [notification level](#notification-levels)
+  which applies to all your notifications.
+- **Receive product marketing emails**: Select this check box to receive periodic
+  emails about GitLab features.
+- **Receive notifications about your own activity**: Select this check box to receive
+  notifications about your own activity. Not selected by default.
 
 ### Notification scope
 
@@ -67,16 +67,16 @@ You can tune the scope of your notifications by selecting different notification
 
 Notification scope is applied in order of precedence (highest to lowest):
 
-- Project
-  - For each project, you can select a notification level. Your project setting overrides the group setting.
-- Group
-  - For each group, you can select a notification level. Your group setting overrides your default setting.
-- Global (default)
-  - Your global, or _default_, notification level applies if you have not selected a notification level for the project or group in which the activity occurred.
+- **Project**: For each project, you can select a notification level. Your project
+  setting overrides the group setting.
+- **Group**: For each group, you can select a notification level. Your group setting
+  overrides your default setting.
+- **Global (default)**: Your global, or _default_, notification level applies if you
+  have not selected a notification level for the project or group in which the activity occurred.
 
 #### Project notifications
 
-You can select a notification level for each project. This can be useful if you need to closely monitor activity in select projects.
+You can select a notification level for each project to help you closely monitor activity in select projects.
 
 ![notification settings](img/notification_project_settings_v12_8.png)