[doc] Fixing underline warnings

4 jobs for doc-cleanup in 8 minutes and 58 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #223740
docker
build_linux_37

00:05:56

83.0%
passed #223741
docker
build_linux_38

00:05:57

83.0%
passed #223738
intel macos
build_macos_intel_37

00:08:56

83.0%
passed #223739
intel macos
build_macos_intel_38

00:08:58

83.0%