[8.8] [Security Solution] Fix a broken header on small screens (#156525)

[kibanamachine]

Backport

This will backport the following commits from main to 8.8:

• [Security Solution] Fix a broken header on small screens (#156525)

Questions ?

Please refer to the Backport tool documentation

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: b444101

Failed CI Steps

• Security Solution Tests #3

Test Failures

• [job] [logs] Security Solution Tests #3 / timeline flyout button the (+) button popover menu owns focus

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
securitySolution	9.1MB	9.1MB	+137.0B

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	17	19	+2
securitySolution	399	402	+3
total			+5

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	18	20	+2
securitySolution	479	482	+3
total			+5

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @maximpn