Bump bootstrap4-api from 4.6.0-2 to 4.6.0-3

Bumps [bootstrap4-api](https://github.com/jenkinsci/bootstrap4-api-plugin) from 4.6.0-2 to 4.6.0-3.
- [Release notes](https://github.com/jenkinsci/bootstrap4-api-plugin/releases)
- [Changelog](https://github.com/jenkinsci/bootstrap4-api-plugin/blob/master/CHANGELOG.md)
- [Commits](jenkinsci/bootstrap4-api-plugin@v4.6.0-2...v4.6.0-3)

Signed-off-by: dependabot[bot] <support@github.com>

plugin/pom.xml

@@ -36,7 +36,7 @@
     <echarts-api.version>5.0.1-1</echarts-api.version>
     <font-awesome-api.version>5.15.2-2</font-awesome-api.version>
     <jquery3-api.version>3.6.0-1</jquery3-api.version>
-    <bootstrap4-api.version>4.6.0-2</bootstrap4-api.version>
+    <bootstrap4-api.version>4.6.0-3</bootstrap4-api.version>
     <popper-api.version>1.16.1-2</popper-api.version>
     <error_prone_annotations.version>2.5.1</error_prone_annotations.version>