Modifies the interface of LanguageModelManager to note that some methods are for testing only.

Source/LanguageModelManager.h

@@ -28,7 +28,6 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface LanguageModelManager : NSObject
 
-+ (void)loadDataModels;
 + (void)loadDataModel:(InputMode)mode;
 + (void)loadUserPhrases;
 + (void)loadUserPhraseReplacement;
@@ -45,4 +44,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
+/// The following methods are merely for testing.
+@interface LanguageModelManager ()
++ (void)loadDataModels;
+@end
+
 NS_ASSUME_NONNULL_END