Improve installation language fallback system

[jolelievre]

Questions	Answers
Branch?	develop
Description?	In installation from browser the fallback when HTTP_ACCEPT_LANGUAGE was not set did not work properly, this is fixed so that we can curl the page correctly in CI workflows
Type?	bug fix
Category?	IN
BC breaks?	no
Deprecations?	no
How to test?	CI green and UI tests green
UI Tests	https://github.com/jolelievre/ga.tests.ui.pr/actions/runs/6480520412
Fixed issue or discussion?	~
Related PRs	~
Sponsor company	@PrestaShopCorp

[prestonBot]

Hi, thanks for this contribution!

I found some issues with the Pull Request description:

• Your pull request does not seem to fix any issue, consider creating one (see note below) and linking it by writing Fixes #1234.

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[florine2623]

@jolelievre , could you relaunch the failed tests please ?
Other than auto tests, there's nothing to test by QA ?

[Progi1984]

@florine2623 No need. We (me and @boubkerbribri) have participed to the PR for validation.

[Progi1984]

@florine2623 : @jolelievre restarted its tests. It's ok.

[prestonBot]

QA approved, well done! Message to the maintainers: do not forget to milestone it before the merge.

[florine2623]

Thanks @Progi1984 and @jolelievre ! OK to merge