Fix typo

Co-Authored-By: Anna Scholtz <anna@scholtzan.net>

script/copy_deduplicate

@@ -4,7 +4,7 @@
 Copy a day's data from live ping tables to stable ping tables,
 deduplicating on document_id.
 
-By default, the script will process all tables in datsets named
+By default, the script will process all tables in datasets named
 like *_live, copying data into table of the same name in *_stable
 datasets. The script can be configured to exclude a list of tables
 or to process only a specific list of tables.