Update md format to make it more easier to read

Before the changes,  the statement of the set-values messed up together, so it is hard to read it out clearly.

Author: cdlliuy

content/en/docs/concepts/overview/working-with-objects/labels.md

@@ -140,10 +140,11 @@ partition
 !partition
 ```
 
-The first example selects all resources with key equal to `environment` and value equal to `production` or `qa`.
-The second example selects all resources with key equal to `tier` and values other than `frontend` and `backend`, and all resources with no labels with the `tier` key.
-The third example selects all resources including a label with key `partition`; no values are checked.
-The fourth example selects all resources without a label with key `partition`; no values are checked.
+* The first example selects all resources with key equal to `environment` and value equal to `production` or `qa`.
+* The second example selects all resources with key equal to `tier` and values other than `frontend` and `backend`, and all resources with no labels with the `tier` key.
+* The third example selects all resources including a label with key `partition`; no values are checked.
+* The fourth example selects all resources without a label with key `partition`; no values are checked.
+
 Similarly the comma separator acts as an _AND_ operator. So filtering resources with a `partition` key (no matter the value) and with `environment` different than  `qa` can be achieved using `partition,environment notin (qa)`.
 The _set-based_ label selector is a general form of equality since `environment=production` is equivalent to `environment in (production)`; similarly for `!=` and `notin`.