google_logging_organization_sink grammar fix (#15480)

Author: Smuger

mmv1/third_party/terraform/website/docs/r/logging_organization_sink.html.markdown

@@ -1,12 +1,12 @@
 ---
 subcategory: "Cloud (Stackdriver) Logging"
 description: |-
-  Manages a organization-level logging sink.
+  Manages an organization-level logging sink.
 ---
 
 # google_logging_organization_sink
 
-Manages a organization-level logging sink. For more information see:
+Manages an organization-level logging sink. For more information see:
 * [API documentation](https://cloud.google.com/logging/docs/reference/v2/rest/v2/organizations.sinks)
 * How-to Guides
     * [Exporting Logs](https://cloud.google.com/logging/docs/export)