Fix link to Contributors section in README

[BaumiCoder]

The dashes are also part of the link to this section in the GitHub webview and without the link does not work on GitHub. Although, the additional dashes could not fix the link for other editors (e.g. VSCodium with "Markdwn All in One" or an JetBrains IDE).

📑 Summary

Fix one link in the Table of Content from Pull Request from #4961.
The badges in the section header are tricky to handle, while linking to the section. This change fix it atleast for the webview here at GitHub.

📏 Design Decisions

Check the link which GitHub creates automatically for the section (click left from the header of the section) and change it to this version in the markdown file.

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added necessary unit/e2e tests.
• 📓 have added documentation. Make sure MERMAID_RELEASE_VERSION is used for all new features.
• 🔖 targeted develop branch

[netlify]

❌ Deploy Preview for mermaid-js failed.

Name	Link
🔨 Latest commit	762113d
🔍 Latest deploy log	https://app.netlify.com/sites/mermaid-js/deploys/65d0fc41dc37c50008f3a51f

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6be91bc) 43.20% compared to head (762113d) 43.20%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #5298   +/-   ##
========================================
  Coverage    43.20%   43.20%           
========================================
  Files           23       23           
  Lines         5115     5115           
  Branches        23       23           
========================================
  Hits          2210     2210           
  Misses        2904     2904           
  Partials         1        1           

Flag	Coverage Δ
unit	43.20% <ø> (ø)

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