Use default branch for build status
<td>
<a href="https://github.com/bokeh/bokeh/actions">
- <img src="https://img.shields.io/github/actions/workflow/status/bokeh/bokeh/bokeh-ci.yml?branch=branch-3.1&label=Bokeh-CI&logo=github&style=for-the-badge"
+ <img src="https://img.shields.io/github/actions/workflow/status/bokeh/bokeh/bokeh-ci.yml?label=Bokeh-CI&logo=github&style=for-the-badge"
alt="Current Bokeh-CI github actions build status" />
</a>
</td>
<td>
<a href="https://github.com/bokeh/bokeh/actions">
- <img src="https://img.shields.io/github/actions/workflow/status/bokeh/bokeh/bokehjs-ci.yml?branch=branch-3.1&label=BokehJS-CI&logo=github&style=for-the-badge"
+ <img src="https://img.shields.io/github/actions/workflow/status/bokeh/bokeh/bokehjs-ci.yml?label=BokehJS-CI&logo=github&style=for-the-badge"
alt="Current BokehJS-CI github actions build status" />
</a>
</td>
