optimize: upgrade elliptic to 6.5.7

[slievrly]

• I have registered the PR changes.

Ⅰ. Describe what this PR did

upgrade elliptic to 6.5.7

Ⅱ. Does this pull request fix one issue?

https://github.com/apache/incubator-seata/security/dependabot/157
https://github.com/apache/incubator-seata/security/dependabot/156
https://github.com/apache/incubator-seata/security/dependabot/155

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.18%. Comparing base (256c4a3) to head (89820aa).
Report is 1 commits behind head on 2.x.

Additional details and impacted files

@@            Coverage Diff            @@
##                2.x    #6787   +/-   ##
=========================================
  Coverage     52.17%   52.18%           
+ Complexity     6292     6291    -1     
=========================================
  Files          1065     1065           
  Lines         37199    37199           
  Branches       4413     4413           
=========================================
+ Hits          19410    19412    +2     
- Misses        15870    15871    +1     
+ Partials       1919     1916    -3     

see 2 files with indirect coverage changes

[funky-eyes]

LGTM