Removal can be tricky, but you can use some custom admin CSS to hide it. My group blocks do not have a layout options section, it must be something added by your theme or plugin. All the same, CSS can hide it, but I cannot provide an exact example. This CSS hides the Advanced section, probably for all blocks:
<style>
.components-panel__body.block-editor-block-inspector__advanced {
display: none;
}
</style>
Since layout is more block specific, proper selectors might possibly only affect the group block. Use your browser’s element inspector tool to help you learn the correct selectors for the layout section.
You can output custom admin CSS inline from the ‘admin_print_styles’ action. Hook the action with a large priority arg so it gets printed after all the other stylesheet references.
