fix(layout): remove some duplicate layout > flex styles

[Splaktar]

PR Checklist

Please check that your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added or this is not a bug fix / enhancement
• Docs have been added, updated, or were not required

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Some styles like .layout-row > .flex-50 are duplicated in the final CSS output.

Issue Number:
Fixes #11609

What is the new behavior?

• removed some duplicate layout > flex styles
• reduced unminified CSS size by 5KB

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information