…y & remove spaceless (arkste)This PR was squashed before being merged into the 3.4 branch (closes#24728).Discussion----------[Bridge\Twig] fix bootstrap checkbox_row to render properly & remove spaceless| Q             | A| ------------- | ---| Branch?       | 3.4| Bug fix?      | yes| New feature?  | no| BC breaks?    | no| Deprecations? | no| Tests pass?   | yes| Fixed tickets |#24711| License       | MIT| Doc PR        | -As discussed in#24711 i reverted the change i did in `bootstrap_3_layout.html.twig` (which caused an unnecessary empty div-container in the vertical-layout), added the `checkbox_row` block to the `bootstrap_3_horizontal_layout.html.twig` and removed `spaceless` (as proposed in#24727).since i added `{#--#}` in bootstrap 3, i did the same for the same horizontal blocks in bootstrap 4 as well.I moved the `form_label_class` & `form_group_class` blocks to the top of `bootstrap_3_horizontal_layout.html.twig` & `bootstrap_4_horizontal_layout.html.twig`, this should improve DX as they were spreaded across the file.#24702 affected the bootstrap 4 horizontal layout as well, so i added the `checkbox_row` block to bootstrap 4 too.ping@fabpot@nicolas-grekasCommits-------f84749f [Bridge\Twig] fix bootstrap checkbox_row to render properly & remove spaceless