minor #27886 [Form] Removed .form-control-label class. (vudaltsov)

This PR was squashed before being merged into the 3.4 branch (closes #27886).

Discussion
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[Form] Removed .form-control-label class.

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

There is no such a class neither in [bootstrap 4.0](https://getbootstrap.com/docs/4.0/components/forms/#form-controls) nor in [bootstrap 4.1](https://getbootstrap.com/docs/4.1/components/forms/#form-controls).

Commits
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cb3e712698 [Form] Removed .form-control-label class.

Author: nicolas-grekas

Resources/views/Form/bootstrap_4_layout.html.twig

@@ -187,7 +187,7 @@
             {%- set element = 'legend' -%}
             {%- set label_attr = label_attr|merge({class: (label_attr.class|default('') ~ ' col-form-label')|trim}) -%}
         {%- else -%}
-            {%- set label_attr = label_attr|merge({for: id, class: (label_attr.class|default('') ~ ' form-control-label')|trim}) -%}
+            {%- set label_attr = label_attr|merge({for: id}) -%}
         {%- endif -%}
         {% if required -%}
             {% set label_attr = label_attr|merge({class: (label_attr.class|default('') ~ ' required')|trim}) %}