Fixes #11797: defaultDesktopBookmarksFoldersTest intermittent failure

[sv-ohorvath]

Assertion failure on the Sign in to sync button.

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features. In addition, it includes a screenshot of a successful accessibility scan to ensure no new defects are added to the product.

After merge

• Milestone: Make sure issues finished by this pull request are added to the milestone of the version currently in development.

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[codecov-commenter]

Codecov Report

Merging #11803 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master   #11803   +/-   ##
=========================================
  Coverage     21.93%   21.93%           
  Complexity      716      716           
=========================================
  Files           376      376           
  Lines         15047    15047           
  Branches       1951     1951           
=========================================
  Hits           3301     3301           
+ Misses        11464    11463    -1     
- Partials        282      283    +1     

Impacted Files	Coverage Δ	Complexity Δ
.../fenix/browser/browsingmode/BrowsingModeManager.kt	85.71% <0.00%> (-14.29%)	0.00% <0.00%> (ø%)
app/src/main/java/org/mozilla/fenix/Config.kt	36.11% <0.00%> (+2.77%)	2.00% <0.00%> (ø%)

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