Update README.md code block format.

[lamtrinhdev]

Update README.md code block format.

• The change/commits follow the Mullvad coding guidelines: https://github.com/mullvad/coding-guidelines
• The PR description should describe:
  • What some of README.md files.
  • Why highlight the syntax in code block.

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This change is 

[lamtrinhdev]

Dear @MarkusPettersson98 ,

As the comment the PR #6558 . Could you please help me to review this PR?

Thanks,
Lam

[lamtrinhdev]

Dear @MarkusPettersson98 ,

Could you help me to review the PR?

Thanks,
Lam

[lamtrinhdev]

Dear @faern ,

As the PR #6670 . I have one more PR waiting to be reviewed. Would you be able to assist me in dedicating time to review it?

Thanks,
Lam

[faern]

I'm not sure this is needed. It makes no practical difference as far as I can see. For the bash blocks, I don't even see any relevant syntax highlighting on Github when rendered.

[lamtrinhdev]

Dear @faern ,

Thank you for your feedback. I will closed this PR.

Thanks,
Lam