Encourage community to create failing PRs for bugs

[scarroll32]

Closes #1464

[Copilot]

Pull Request Overview

Updates documentation to encourage community members to submit pull requests with failing tests instead of creating bug report templates when reporting issues.

• Removes bug report template files from the repository
• Updates documentation across README, CONTRIBUTING.md, and intro.md to request failing tests in PRs
• Modifies CHANGELOG.md entries to reflect the new approach

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/docs/intro.md	Changes guidance from "branch with failing spec" to "pull request with failing test"
bug_report_templates/test-ransacker-arel-present-predicate.rb	Removes bug report template file
bug_report_templates/test-ransack-scope-and-column-same-name.rb	Removes bug report template file
README.md	Updates bug reporting guidance to request failing test PRs
CONTRIBUTING.md	Replaces bug report template instructions with failing test guidance
CHANGELOG.md	Updates changelog entries to reflect the new approach

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