doc: correct formatting of example definitions for --test-shard

PR-URL: #58571
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: JakobJingleheimer

doc/api/cli.md

@@ -2578,8 +2578,9 @@ added:
 
 Test suite shard to execute in a format of `<index>/<total>`, where
 
-`index` is a positive integer, index of divided parts
-`total` is a positive integer, total of divided part
+* `index` is a positive integer, index of divided parts.
+* `total` is a positive integer, total of divided part.
+
 This command will divide all tests files into `total` equal parts,
 and will run only those that happen to be in an `index` part.