Fix asv benchmark action

[luizirber]

Oops, it was not comparing the current PR against master, but the two previous commits in master to each other...

Checklist

• Is it mergeable?
• make test Did it pass the tests?
• make coverage Is the new code covered?
• Did it change the command-line interface? Only additions are allowed
  without a major version increment. Changing file formats also requires a
  major version number increment.
• Was a spellchecker run on the source code and documentation after
  changes were made?

[luizirber]

Ready for review and merge @ctb

[codecov]

Codecov Report

Merging #759 into master will increase coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #759      +/-   ##
==========================================
+ Coverage   88.29%   88.42%   +0.12%     
==========================================
  Files          30       30              
  Lines        4785     4786       +1     
  Branches       46       46              
==========================================
+ Hits         4225     4232       +7     
+ Misses        557      551       -6     
  Partials        3        3

Impacted Files	Coverage Δ
sourmash/sbt_storage.py	85.39% <0%> (-0.98%)	⬇️
sourmash/sbt.py	85.53% <0%> (+0.31%)	⬆️
sourmash/lca/command_index.py	90.7% <0%> (+0.44%)	⬆️
sourmash/lca/lca_utils.py	96.01% <0%> (+0.79%)	⬆️
sourmash/signature_json.py	97.19% <0%> (+1.12%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 21f4894...e0b9aa0. Read the comment docs.