docs: Fix incorrect links (#3242)

Author: zawataki

docs/tutorials/getting-started-mysql.md

@@ -222,4 +222,4 @@ $ sqlc push --tag tutorial
 
 In the sidebar, go to the "Insights" section to run checks against your queries.
 If you need access to a pre-configured MySQL database, check out [managed
-databases](../howtwo/managed-databases.md).
+databases](../howto/managed-databases.md).

docs/tutorials/getting-started-postgresql.md

@@ -242,4 +242,4 @@ $ sqlc push --tag tutorial
 
 In the sidebar, go to the "Insights" section to run checks against your queries.
 If you need access to a pre-configured PostgreSQL database, check out [managed
-databases](../howtwo/managed-databases.md).
+databases](../howto/managed-databases.md).