Fixes dunstctl history command

[stremlenye]

Removes -l option from the busctl invocation since it's only relevant to the list outputs.
That fixes the command to fail on invocation with an internal error

busctl: invalid option -- 'l'

See buctl(1)

[fwsmit]

Weird that it didn't give that error earlier

[codecov-commenter]

Codecov Report

Merging #1060 (4fee122) into master (8aaa019) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1060   +/-   ##
=======================================
  Coverage   61.30%   61.30%           
=======================================
  Files          45       45           
  Lines        7097     7097           
=======================================
  Hits         4351     4351           
  Misses       2746     2746           

Flag	Coverage Δ
unittests	61.30% <ø> (ø)

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[fwsmit]

For me the dunstctl history command works, but it seems like removing the -l can't hurt, so I'll merge this PR. Thank you!