Switch additional testing to JDK 26

We will soon move to JDK 25 in the runtime so we can start testing with JDK 26.

Author: wendigo

.github/workflows/ci.yml

@@ -58,7 +58,7 @@ jobs:
       matrix:
         include:
           - { java-version: 24, cache: 'true', cleanup-node: true }
-          - { java-version: 25-ea, cache: 'restore', cleanup-node: true }
+          - { java-version: 26-ea, cache: 'restore', cleanup-node: true }
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v5