dot-dsl: remove dependency in test code

exercises/practice/dot-dsl/Cargo.toml

@@ -2,6 +2,3 @@
 edition = "2021"
 name = "dot-dsl"
 version = "0.1.0"
-
-[dependencies]
-maplit = "1.0.1"

exercises/practice/dot-dsl/tests/dot-dsl.rs

@@ -1,7 +1,8 @@
+use std::collections::HashMap;
+
 use dot_dsl::graph::graph_items::edge::Edge;
 use dot_dsl::graph::graph_items::node::Node;
 use dot_dsl::graph::Graph;
-use maplit::hashmap;
 
 #[test]
 fn empty_graph() {
@@ -81,9 +82,7 @@ fn graph_with_one_edge_with_keywords() {
 fn graph_with_one_attribute() {
     let graph = Graph::new().with_attrs(&[("foo", "1")]);
 
-    let expected_attrs = hashmap! {
-        "foo".to_string() => "1".to_string(),
-    };
+    let expected_attrs = HashMap::from([("foo".to_string(), "1".to_string())]);
 
     assert!(graph.nodes.is_empty());
 
@@ -108,11 +107,11 @@ fn graph_with_attributes() {
 
     let attrs = vec![("foo", "1"), ("title", "Testing Attrs"), ("bar", "true")];
 
-    let expected_attrs = hashmap! {
-        "foo".to_string() => "1".to_string(),
-        "title".to_string() => "Testing Attrs".to_string(),
-        "bar".to_string() => "true".to_string(),
-    };
+    let expected_attrs = HashMap::from([
+        ("foo".to_string(), "1".to_string()),
+        ("title".to_string(), "Testing Attrs".to_string()),
+        ("bar".to_string(), "true".to_string()),
+    ]);
 
     let graph = Graph::new()
         .with_nodes(&nodes)