GH-44830: [Java][CI] Disable Java Dependabot (#44832)

### Rationale for this change

We moved to apache/arrow-java.

### What changes are included in this PR?

Stop running Dependabot for Maven here.

### Are these changes tested?

N/A

### Are there any user-facing changes?

No.
* GitHub Issue: #44830

Authored-by: David Li <li.davidm96@gmail.com>
Signed-off-by: Raúl Cumplido <raulcumplido@gmail.com>

.github/dependabot.yml

@@ -24,13 +24,6 @@ updates:
     commit-message:
       prefix: "MINOR: [CI] "
     open-pull-requests-limit: 10
-  - package-ecosystem: "maven"
-    directory: "/java/"
-    schedule:
-      interval: "weekly"
-    commit-message:
-      prefix: "MINOR: [Java] "
-    open-pull-requests-limit: 10
   - package-ecosystem: "npm"
     directory: "/js/"
     schedule: