Clean up README by removing unused badges

Removed several badge images from the README.

Author: MatALass

README.md

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 ![CI](https://github.com/MatALass-ISM/ects-grade-engine/actions/workflows/ci.yml/badge.svg)
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 ![PostgreSQL](https://img.shields.io/badge/PostgreSQL-15-blue)
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 ![MySQL](https://img.shields.io/badge/MySQL-8-orange)
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 ![SQLFluff](https://img.shields.io/badge/Linted_with-sqlfluff-purple)
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 ![License](https://img.shields.io/github/license/MatALass-ISM/ects-grade-engine)
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 ![Last Commit](https://img.shields.io/github/last-commit/MatALass-ISM/ects-grade-engine)
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-![Repo Size](https://img.shields.io/github/repo-size/MatALass-ISM/ects-grade-engine)
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 ![Issues](https://img.shields.io/github/issues/MatALass-ISM/ects-grade-engine)
 
-![Stars](https://img.shields.io/github/stars/MatALass-ISM/ects-grade-engine?style=social)
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 # ects-grade-engine
 
 > Production-ready SQL model to assign ECTS grades (A--E) based on GPA