Docs: remove no longer active lgtm badges

Signed-off-by: Cleber Rosa <[email protected]>

docs/source/quickstart/index.rst

@@ -249,22 +249,10 @@ Build and Quality Status
    :target: https://cirrus-ci.com/github/avocado-framework/avocado
    :alt: Basic checks on Cirrus CI
 
-.. image:: https://img.shields.io/lgtm/alerts/g/avocado-framework/avocado.svg?logo=lgtm&logoWidth=18
-   :target: https://lgtm.com/projects/g/avocado-framework/avocado/alerts/
-   :alt: lgtm total alerts
-
 .. image:: https://api.codeclimate.com/v1/badges/03f506164e1d19f95480/maintainability
    :target: https://codeclimate.com/github/avocado-framework/avocado/maintainability
    :alt: Code Climate Maintainability
 
-.. image:: https://img.shields.io/lgtm/grade/python/g/avocado-framework/avocado.svg?logo=lgtm&logoWidth=18
-   :target: https://lgtm.com/projects/g/avocado-framework/avocado/context:python
-   :alt: lgtm language grade for Python
-
-.. image:: https://img.shields.io/lgtm/grade/javascript/g/avocado-framework/avocado.svg?logo=lgtm&logoWidth=18
-   :target: https://lgtm.com/projects/g/avocado-framework/avocado/context:javascript
-   :alt: lgtm language grade for JavaScript
-
 .. image:: https://readthedocs.org/projects/avocado-framework/badge/?version=latest
    :target: https://avocado-framework.readthedocs.io/en/latest/
    :alt: Documentation Status