chore(hybridcloud) Add sentry_region to flagpole docs (#1318)

src/docs/feature-flags/flagpole.mdx

@@ -104,6 +104,12 @@ Each context builder consists of a list of context transformers, which are respo
 
 Here are some common properties we surface via our Sentry and GetSentry context builders that you can use in your conditions:
 
+**System Context Properties**
+
+`sentry_region` [str]
+
+: The sentry region or single-tenant the flag check is being perfomed in.
+
 **Organization Context Properties**
 
 `organization_id` [int]
@@ -144,12 +150,11 @@ Here are some common properties we surface via our Sentry and GetSentry context
 
 
 To see the latest context properties available, check out the repo-specific context builders:
-- [Sentry Context Builder](https://github.com/getsentry/sentry/blob/master/src/sentry/features/flagpole_context.py)
 
+- [Sentry Context Builder](https://github.com/getsentry/sentry/blob/master/src/sentry/features/flagpole_context.py)
 - [GetSentry Context Builder](https://github.com/getsentry/getsentry/blob/master/getsentry/feature_handlers/getsentry_flagpole_context_builder.py)
 
 
-
 ## Rolling out a new Flagpole feature
 
 Creating a new Flagpole Feature is currently a 3 step process:
@@ -218,4 +223,4 @@ active in your local devserver instance and will persist across runs until
 you remove the feature option.
 
 To unset your feature, comment out or remove your feature config from the
-`option` object, and rerun the `getsentry configoptions` command above.
+`option` object, and rerun the `getsentry configoptions` command above.