Rename default_namespace_setting documentation to correct name (#3682)

* Rename default_namespace_setting documentation to correct name

* Update title of databricks_default_namespace_setting

Author: al-lac

docs/resources/default_namespace_settings.md renamed to docs/resources/default_namespace_setting.md

@@ -2,7 +2,7 @@
 subcategory: "Settings"
 ---
 
-# databricks_namespace_setting Resource
+# databricks_default_namespace_setting Resource
 
 -> **Note** This resource could be only used with workspace-level provider!