Update lightning_cli.rst

[loic-beheshti]

Much better with a comma :)

What does this PR do?

Fixes #<issue_number>

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[codecov]

Codecov Report

Merging #7554 (87914b3) into master (6ac16ff) will decrease coverage by 0%.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #7554   +/-   ##
======================================
- Coverage      88%     88%   -0%     
======================================
  Files         196     196           
  Lines       12835   12835           
======================================
- Hits        11286   11270   -16     
- Misses       1549    1565   +16