Replace GitHub build for Java 15 with Java 16 and drop Java 16-ea.
diff --git a/.github/workflows/maven.yml b/.github/workflows/maven.yml
index f0933eb..08d8b8e 100644
--- a/.github/workflows/maven.yml
+++ b/.github/workflows/maven.yml
@@ -24,11 +24,9 @@
     continue-on-error: ${{ matrix.experimental }}

     strategy:

       matrix:

-        java: [ 8, 11, 15 ]

+        java: [ 8, 11, 16 ]

         experimental: [false]

         include:

-          - java: 16-ea

-            experimental: true        

           - java: 17-ea

             experimental: true