Fix type annotation of arg options

[kiharito]

Hello. Thank you for your maintenance.

This PR fixes the type annotation of the argument options in the method that sets range key.

[andrykonchin]

Thank you!

[codecov]

Codecov Report

Merging #691 (e16730c) into master (f8fb70c) will not change coverage.
The diff coverage is n/a.

❗ Current head e16730c differs from pull request most recent head d3a9f3c. Consider uploading reports for the commit d3a9f3c to get more accurate results

@@           Coverage Diff           @@
##           master     #691   +/-   ##
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  Coverage   90.35%   90.35%           
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  Files          62       62           
  Lines        3162     3162           
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  Hits         2857     2857           
  Misses        305      305           

Files	Coverage Δ
lib/dynamoid/fields.rb	100.00% <ø> (ø)