Fixed broken link in gh-actions badge (#2325)

* Fixed broken link in gh-actions badge

* Update README.md

Co-authored-by: Philipp Rudiger <prudiger@anaconda.com>

README.md

@@ -6,7 +6,7 @@
 
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-| Build Status | [![Linux/MacOS Build Status](https://github.com/holoviz/panel/workflows/pytest/badge.svg)](https://github.com/holoviz/panel/workflows/pytest)
+| Build Status | [![Linux/MacOS Build Status](https://github.com/holoviz/panel/workflows/pytest/badge.svg?query=branch%3Amaster)](https://github.com/holoviz/panel/actions/workflows/test.yaml?query=branch%3Amaster)
 | Coverage | [![codecov](https://codecov.io/gh/holoviz/panel/branch/master/graph/badge.svg)](https://codecov.io/gh/holoviz/panel) |
 | Latest dev release | [![Github tag](https://img.shields.io/github/v/tag/holoviz/panel.svg?label=tag&colorB=11ccbb)](https://github.com/holoviz/panel/tags) [![dev-site](https://img.shields.io/website-up-down-green-red/https/pyviz-dev.github.io/panel.svg?label=dev%20website)](https://pyviz-dev.github.io/panel/) |
 | Latest release | [![Github release](https://img.shields.io/github/release/holoviz/panel.svg?label=tag&colorB=11ccbb)](https://github.com/holoviz/panel/releases) [![PyPI version](https://img.shields.io/pypi/v/panel.svg?colorB=cc77dd)](https://pypi.python.org/pypi/panel) [![panel version](https://img.shields.io/conda/v/pyviz/panel.svg?colorB=4488ff&style=flat)](https://anaconda.org/pyviz/panel) [![conda-forge version](https://img.shields.io/conda/v/conda-forge/panel.svg?label=conda%7Cconda-forge&colorB=4488ff)](https://anaconda.org/conda-forge/panel) [![defaults version](https://img.shields.io/conda/v/anaconda/panel.svg?label=conda%7Cdefaults&style=flat&colorB=4488ff)](https://anaconda.org/anaconda/panel) |