Corrected the argument in super().__init__() within SplashAwareDupeFilter's __init__()

[protokoul]

Submitting this PR to resolve a bug highlighted here #322 (comment). RFPDupeFilter's __init__() implements fingerprinter as a keyword-only argument.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 91.18%. Comparing base (d763eb7) to head (159dc60).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
scrapy_splash/dupefilter.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #328   +/-   ##
=======================================
  Coverage   91.18%   91.18%           
=======================================
  Files           9        9           
  Lines         681      681           
  Branches      125      125           
=======================================
  Hits          621      621           
  Misses         36       36           
  Partials       24       24           

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