chore(README): update the badge from obsolete build to active main

Signed-off-by: Krisztian Szilvasi <34309983+kr-t@users.noreply.github.com>

Author: kr-t

README.md

@@ -7,7 +7,7 @@ SPDX-License-Identifier: Apache-2.0 -->
 
 # Ocre
 
-[![Build](https://github.com/project-ocre/ocre-runtime/actions/workflows/build.yml/badge.svg)](https://github.com/project-ocre/ocre-runtime/actions/workflows/build.yml)
+[![Main](https://github.com/project-ocre/ocre-runtime/actions/workflows/main.yml/badge.svg)](https://github.com/project-ocre/ocre-runtime/actions/workflows/main.yml)
 [![OpenSSF Best Practices](https://www.bestpractices.dev/projects/9691/badge)](https://www.bestpractices.dev/projects/9691)
 [![License](https://img.shields.io/github/license/project-ocre/ocre-runtime?color=blue)](LICENSE)
 [![slack](https://img.shields.io/badge/slack-ocre-brightgreen.svg?logo=slack)](https://lfedge.slack.com/archives/C07F190CC3X)