ORC-2112: Use Java 25 for Ubuntu 26.04 docker test

### What changes were proposed in this pull request?

This PR aims to use `Java 25` for `Ubuntu 26.04` docker test.

### Why are the changes needed?

To have `Java 25` test coverage on `Ubuntu 26.04`.

### How was this patch tested?

Pass the CIs. The image was published already.

```bash
$ docker run -it --rm apache/orc-dev:ubuntu26 java --version
openjdk 25.0.2 2026-01-20
OpenJDK Runtime Environment (build 25.0.2+10-Ubuntu-1)
OpenJDK 64-Bit Server VM (build 25.0.2+10-Ubuntu-1, mixed mode, sharing)
```

### Was this patch authored or co-authored using generative AI tooling?

Generated-by: `Gemini 3.1 Pro (High)` on `Antigravity`

Closes #2557 from dongjoon-hyun/ORC-2112.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>
(cherry picked from commit 93b0997)
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

Author: dongjoon-hyun

docker/ubuntu26/Dockerfile

@@ -22,7 +22,7 @@ LABEL org.opencontainers.image.authors="Apache ORC project <dev@orc.apache.org>"
 LABEL org.opencontainers.image.licenses="Apache-2.0"
 LABEL org.opencontainers.image.ref.name="Apache ORC on Ubuntu 26"
 LABEL org.opencontainers.image.version=""
-ARG jdk=21
+ARG jdk=25
 ARG cc=gcc
 
 RUN apt-get update