fix flaky streams map test on Windows

[marten-seemann]

Fixes #3008.

Can't really reproduce it locally, but it certainly won't hurt to increase the Eventually timeout to its default value.

[codecov]

Codecov Report

Merging #3013 (08f7cce) into master (53b1cbb) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3013   +/-   ##
=======================================
  Coverage   86.13%   86.13%           
=======================================
  Files         135      135           
  Lines        9455     9455           
=======================================
  Hits         8144     8144           
  Misses        952      952           
  Partials      359      359           

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