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

doc: correct formatting of example definitions for `--test-shard` · nodejs/node@447ca11

Original file line number	Diff line number	Diff line change
`@@ -2574,8 +2574,9 @@ added:`
`2574`	`2574`
`2575`	`2575`	Test suite shard to execute in a format of `<index>/<total>`, where
`2576`	`2576`
`2577`		-`index` is a positive integer, index of divided parts
`2578`		-`total` is a positive integer, total of divided part
	`2577`	+* `index` is a positive integer, index of divided parts.
	`2578`	+* `total` is a positive integer, total of divided part.
	`2579`	`+`
`2579`	`2580`	This command will divide all tests files into `total` equal parts,
`2580`	`2581`	and will run only those that happen to be in an `index` part.
`2581`	`2582`