update the Heart library to v9.0.0

Author: stephengold

common.gradle

@@ -9,7 +9,7 @@ ext {
 
     // module coordinates of external dependencies:
     acorusCoordinates = 'com.github.stephengold:Acorus:1.1.1'
-    heartCoordinates = 'com.github.stephengold:Heart:8.8.0'
+    heartCoordinates = 'com.github.stephengold:Heart:9.0.0'
 
     // current versions of libraries:
     jme3utilitiesniftyVersion = '0.9.37-SNAPSHOT'