Remove SonarCube from the build pipeline

[rhr323]

This PR removes Sonarcube from the build pipeline, as well as any additional references to Sonarcube.

See also: groups.google.com/a/elastic.co/g/dev/c/m6DbmHI6wy0

Rel: elasticco.atlassian.net/browse/CPSERV-875

(Reopened #201 against main instead of against a fork)

[Copilot]

Pull Request Overview

This PR removes SonarQube static code analysis from the build pipeline and eliminates all related configuration references. The purpose is to decommission SonarQube integration from the project's CI/CD workflow.

• Removes the entire SonarQube configuration file
• Eliminates SonarQube step from Buildkite pipeline
• Removes SonarQube project metadata from catalog configuration

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
sonar-project.properties	Complete removal of SonarQube project configuration
catalog-info.yaml	Removes SonarQube project key annotation from metadata
.buildkite/pipeline.yml	Removes SonarQube static code analysis step from CI pipeline

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