fix mock pkgs in docs

[Borda]

What does this PR do?

Update mocking pkgs according to fix from Bolts Lightning-Universe/lightning-bolts#234

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[codecov]

Codecov Report

Merging #4591 (fdeba70) into master (343d19f) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #4591   +/-   ##
======================================
  Coverage      93%     93%           
======================================
  Files         116     116           
  Lines        8858    8858           
======================================
  Hits         8253    8253           
  Misses        605     605           

[SkafteNicki]

LGTM