fuzz: adapt target to number of keywords being dynamic

[catenacyber]

Link to ticket: https://redmine.openinfosecfoundation.org/issues/
https://redmine.openinfosecfoundation.org/issues/4683
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=69727&q=label%3AProj-suricata
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=69725&q=label%3AProj-suricata

Describe changes:

• fuzz: adapt target to number of keywords being dynamic

Follow up on 4bbe7d9

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.47%. Comparing base (49ecf37) to head (aa12c9d).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #11317   +/-   ##
=======================================
  Coverage   82.47%   82.47%           
=======================================
  Files         934      934           
  Lines      252270   252270           
=======================================
+ Hits       208055   208066   +11     
+ Misses      44215    44204   -11     

Flag	Coverage Δ
fuzzcorpus	60.26% <ø> (ø)
livemode	18.76% <ø> (+<0.01%)	⬆️
pcap	43.79% <ø> (+0.01%)	⬆️
suricata-verify	61.31% <ø> (-0.01%)	⬇️
unittests	59.92% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[victorjulien]

Merged in #11320, thanks!