Fix broken GitHub tarball download link in installation guide

[iihimanshuu]

Description

Fix malformed tarball download URL in installation documentation.

Changed:

• https://github.com/osl-incubator/sugar.git/tarball/main

• https://github.com/osl-incubator/sugar/tarball/main

The .git extension in the middle of the URL was preventing users from downloading the source code archive. This fixes both the documentation link reference and the curl command example.

Pull Request checklists

This PR is a:

• bug-fix
• new feature
• maintenance

About this PR:

• it includes tests.
• the tests are executed on CI.
• the tests generate log file(s) (path).
• pre-commit hooks were executed locally.
• this PR requires a project documentation update.

Author's checklist:

• I have reviewed the changes and it contains no misspelling.
• The code is well commented, especially in the parts that contain more
  complexity.
• New and old tests passed locally.

Additional information

Reviewer's checklist

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## Reviewer's Checklist

- [ ] I managed to reproduce the problem locally from the `main` branch
- [ ] I managed to test the new changes locally
- [ ] I confirm that the issues mentioned were fixed/resolved .

[sanjay7178]

LGTM