[Issue] Fix variable name in catalogsearch

[m2-assistant]

This issue is automatically created based on existing pull request: #33533: Fix variable name in catalogsearch

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Fix variable name, the search engine has nothing to do with a default country.
PR Update: I've removed the unneccessary variable. Thanks for the idea @tzyganu ;-)

Description (*)

It's a bit strange and confusing to use a variable called $defaultCountry in the search engine module.
I've renamed removed the variable, there's no change in the behavior/logic of the method.

Fixed Issues (if relevant)

none

Manual testing scenarios (*)

Change Search Engine in the magento admin panel:
Stores > Settings > Configuration > Catalog > Catalog > Catalog Search

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)

[github-jira-sync-bot]

✅ Jira issue https://jira.corp.adobe.com/browse/AC-9215 is successfully created for this GitHub issue.

[m2-assistant]

✅ Confirmed by @engcom-Lima. Thank you for verifying the issue.
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