docs: remove unused badges (#2849)

The lint and test badges reference older GH workflows.

README.md

@@ -4,9 +4,6 @@
 [![mdBook Specs](https://img.shields.io/badge/mdBook-specs-blue)](https://celestiaorg.github.io/celestia-app/)
 [![GitHub Release](https://img.shields.io/github/v/release/celestiaorg/celestia-app)](https://github.com/celestiaorg/celestia-app/releases/latest)
 [![Go Report Card](https://goreportcard.com/badge/github.com/celestiaorg/celestia-app)](https://goreportcard.com/report/github.com/celestiaorg/celestia-app)
-[![Lint](https://github.com/celestiaorg/celestia-app/actions/workflows/lint.yml/badge.svg)](https://github.com/celestiaorg/celestia-app/actions/workflows/lint.yml)
-[![Tests / Code Coverage](https://github.com/celestiaorg/celestia-app/actions/workflows/test.yml/badge.svg)](https://github.com/celestiaorg/celestia-app/actions/workflows/test.yml)
-[![codecov](https://codecov.io/gh/celestiaorg/celestia-app/branch/main/graph/badge.svg?token=CWGA4RLDS9)](https://app.codecov.io/gh/celestiaorg/celestia-app/tree/main)
 [![GitPOAP Badge](https://public-api.gitpoap.io/v1/repo/celestiaorg/celestia-app/badge)](https://www.gitpoap.io/gh/celestiaorg/celestia-app)
 
 celestia-app is a blockchain application built using parts of the Cosmos stack. celestia-app uses