Migrate from LGTM.com to GitHub Code Scanning

[tanzislam]

• https://github.blog/2022-08-15-the-next-step-for-lgtm-com-github-code-scanning/
• https://docs.github.com/en/code-security/code-scanning/automatically-scanning-your-code-for-vulnerabilities-and-errors/setting-up-code-scanning-for-a-repository#setting-up-code-scanning-manually

[tanzislam]

Removed LGTM badge and config in 477767b.