[Docs] Incorrect Upstream Repository Link in CONTRIBUTING-gitflow.md

[GARY121github]

The upstream repository mentioned in the "Add 'upstream' repo to list of remotes" section of CONTRIBUTING-git-flow.md contains an incorrect example link:

git remote add upstream https://github.com/layer5io/meshery.git
While "meshery" is used as an example, it might be misleading. The documentation should indicate that users need to replace this with the actual upstream repository they are contributing to.

Suggested Fix:

Add a placeholder such as https://github.com/layer5io/sistent.git instead of the hardcoded example.
Provide a clear note reminding users to update the repository URL based on their fork.

Example correction:

git remote add upstream https://github.com/layer5io/sistent.git
This will prevent confusion for new contributors and ensure they correctly set up their remotes.

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Contributor Guides and Resources

• 📚 Instructions for contributing to documentation
  • Meshery documentation site and source
• 🛠 Meshery Build & Release Strategy
• 🎨Wireframes and designs for Sistent site in Figma (open invite)
• 🙋🏾🙋🏼 Questions: Layer5 Discussion Forum and Layer5 Community Slack