fix tests with the new pydot release (#10567)

tests/unit/command/test_dag.py

@@ -133,7 +133,7 @@ def test_show_dot(repo):
         "\"stage: 'b.dvc'\" -> \"stage: '2'\";",
         "\"stage: 'b.dvc'\" -> \"stage: '3'\";",
         "\"stage: 'b.dvc'\";",
-        "strict digraph  {",
+        "strict digraph {",
         "}",
     ]
     actual = sorted(line.rstrip() for line in _show_dot(repo.index.graph).splitlines())
@@ -153,7 +153,7 @@ def test_show_dot_properly_escapes():
     )
 
     expected = {
-        "strict digraph  {",
+        "strict digraph {",
         '"data\\raw\\2.dvc";',
         '"prepare";',
         '"4";',