[SPARK-53988] Upgrade Spotless to 8.0.0

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

This PR aims to upgrade `Spotless` to 8.0.0 and remove `google-java-format` setting because it's equal to the default now.

### Why are the changes needed?

To bring the latest improvements and bug fixes:
- https://github.com/diffplug/spotless/releases/tag/gradle%2F8.0.0
  - diffplug/spotless#2540
  - diffplug/spotless#2345
  - diffplug/spotless#2404

### Does this PR introduce _any_ user-facing change?

No. This is a test change.

### How was this patch tested?

Pass the CIs.

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

No.

Closes #399 from dongjoon-hyun/SPARK-53988.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

Author: dongjoon-hyun

build.gradle

@@ -109,7 +109,6 @@ subprojects {
   spotless {
     java {
       endWithNewline()
-      googleJavaFormat('1.28.0')
       importOrder(
         'java',
         'javax',

gradle/libs.versions.toml

@@ -33,7 +33,7 @@ checkstyle = "10.23.1"
 pmd = "7.17.0"
 spotbugs-tool = "4.9.6"
 spotbugs-plugin = "6.4.2"
-spotless-plugin = "6.25.0"
+spotless-plugin = "8.0.0"
 
 # Packaging
 cyclonedx = "2.4.1"