Fix windows-only test failure added in #997

[TheBlueMatt]

This is a trivial bugfix to add a missing test updated required in
PR 997.

[codecov]

Codecov Report

Merging #1091 (a233780) into main (2cf42aa) will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1091      +/-   ##
==========================================
+ Coverage   90.72%   90.77%   +0.04%     
==========================================
  Files          65       65              
  Lines       34212    34354     +142     
==========================================
+ Hits        31039    31185     +146     
+ Misses       3173     3169       -4     

Impacted Files	Coverage Δ
lightning-persister/src/lib.rs	94.21% <ø> (ø)
lightning/src/ln/functional_tests.rs	97.45% <0.00%> (+0.09%)	⬆️
lightning-block-sync/src/http.rs	94.77% <0.00%> (+1.25%)	⬆️

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[ariard]

ACK a233780