Improve documentation

lib/src/score_emitter.dart

@@ -15,7 +15,7 @@ class PrintEmitter implements ScoreEmitter {
   }
 }
 
-/// New interface for [ScoreEmitter]. [ScoreEmitter] will be migrated to
+/// New interface for [ScoreEmitter]. [ScoreEmitter] will be changed to
 /// this interface in the next major version release, and this class will
 /// be deprecated and removed.  That release will be a breaking change.
 abstract class ScoreEmitterV2 implements ScoreEmitter {
@@ -25,7 +25,7 @@ abstract class ScoreEmitterV2 implements ScoreEmitter {
 }
 
 /// New implementation of [PrintEmitter] implementing the [ScoreEmitterV2]
-/// interface.  [PrintEmitter] will be updated to this implementation in the
+/// interface.  [PrintEmitter] will be changed to this implementation in the
 /// next major version release.
 class PrintEmitterV2 implements ScoreEmitterV2 {
   const PrintEmitterV2();