Update punctuations for list items in accordance with style guide

doc/development/background_migrations.md

@@ -300,10 +300,10 @@ for more details.
 ## Best practices
 
 1. Make sure to know how much data you're dealing with
-1. Make sure that background migration jobs are idempotent.
-1. Make sure that tests you write are not false positives.
+1. Make sure that background migration jobs are idempotent
+1. Make sure that tests you write are not false positives
 1. Make sure that if the data being migrated is critical and cannot be lost, the
-   clean-up migration also checks the final state of the data before completing.
+   clean-up migration also checks the final state of the data before completing
 1. Make sure to know how much time it'll take to run all scheduled migrations
 1. When migrating many columns, make sure it won't generate too many
    dead tuples in the process (you may need to directly query the number of dead tuples