Fix typo

Author: nilaybhatia

tests/test_value_tracker.py

@@ -1,13 +1,13 @@
 from manim.mobject.value_tracker import ValueTracker
 
 def test_value_tracker_set_value():
-    """Test ValueTracker.set_value"""
+    """Test ValueTracker.set_value()"""
     tracker = ValueTracker()
     tracker.set_value(10.0)
     assert tracker.get_value() == 10.0
 
 def test_value_tracker_get_value():
-    """Test ValueTracker.get_value"""
+    """Test ValueTracker.get_value()"""
     tracker = ValueTracker(10.0)
     assert tracker.get_value() == 10.0