fix(docs): correct typos and improve formatting in README.md

[henchaves]

Description

This PR updates the README.md file, fixing typos and improving formatting.

Type of Change

• 📚 Examples / docs / tutorials / dependencies update
• 🔧 Bug fix (non-breaking change which fixes an issue)
• 🥂 Improvement (non-breaking change which improves an existing feature)
• 🚀 New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🔐 Security fix

[gemini-code-assist]

Code Review

This pull request updates the README by fixing typos, improving formatting, and promoting giskard-checks to Beta status. It also simplifies a code example by removing a parameter and deletes the "Current sponsors" section. Feedback indicates that the removal of the sponsors section may be accidental or out of scope for this PR, and a suggestion was made to reduce excessive padding in the Markdown table to improve source code readability.

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README.md (177-187)

The "Current sponsors" section has been entirely removed in this PR. Since the PR's stated goal is to "correct typos and improve formatting," this significant content change seems out of scope and might be accidental. If these companies are still sponsoring the project, please restore this section.

README.md (44-48)

The table formatting in this section uses excessive padding for the Description column, which makes the raw Markdown file difficult to read and maintain. While some formatters do this automatically, it's generally better to keep the padding to a minimum (e.g., one space) to improve source code readability.

| Status         | Package          | Description |
| -------------- | ---------------- | ----------- |
| ✅ Beta        | `giskard-checks` | Testing & evaluation — scenario API, built-in checks, LLM-as-judge |
| 🚧 In progress | `giskard-scan`   | Agent vulnerability scanner — red teaming, prompt injection, data leakage (successor of [v2 Scan](https://legacy-docs.giskard.ai/en/stable/open_source/scan/index.html)) |
| 📋 Planned     | `giskard-rag`    | RAG evaluation & synthetic data generation (successor of [v2 RAGET](https://legacy-docs.giskard.ai/en/stable/open_source/testset_generation/index.html)) |