query format fixes

Author: JPryce-Aklundh

modules/ROOT/pages/expressions/list-expressions.adoc

@@ -519,7 +519,7 @@ The below query iterates over the `skills` property of each `Person` node and cr
 // tag::expressions_list_comprehension_properties[]
 [source, cypher]
 ----
-MATCH (p:Person) WHERE p.skills IS NOT null
+MATCH (p:Person) WHERE p.skills IS NOT NULL
 ORDER BY p.name
 RETURN p.name AS name,
       [skill IN p.skills | skill + " expert"] AS modifiedSkills
@@ -568,7 +568,7 @@ List comprehension can be used to remove any unknown `null` values when concaten
 // tag::expressions_list_comprehension_concatenation_remove_null[]
 [source, cypher]
 ----
-RETURN [x IN ([1, null, 3] || [null, 5, null]) WHERE x IS NOT null] AS listWithoutNull
+RETURN [x IN ([1, null, 3] || [null, 5, null]) WHERE x IS NOT NULL] AS listWithoutNull
 ----
 // end::expressions_list_comprehension_concatenation_remove_null[]