Bump build-plugins from 2026.3 to 2026.4

Bumps `build-plugins` from 2026.3 to 2026.4.

Updates `io.openapiprocessor.build.plugin.publish` from 2026.3 to 2026.4

Updates `io.openapiprocessor.build.plugin.create-versions` from 2026.3 to 2026.4

---
updated-dependencies:
- dependency-name: io.openapiprocessor.build.plugin.publish
  dependency-version: '2026.4'
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: io.openapiprocessor.build.plugin.create-versions
  dependency-version: '2026.4'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -8,7 +8,7 @@ bytebuddy = "1.18.11"
 
 # plugins
 updates = "0.54.0"
-build-plugins = "2026.3"
+build-plugins = "2026.4"
 pubplug = "2.1.1"
 
 [libraries]