fix: speed up transaction signing by removing code that does nothing

[steveluscher]

Problem

This _verifySignatures() step runs verification, returns the result of that verification to nobody, and does nothing. We're essentially paying the cost of Message#serialize and Transaction#_verifySignatures and then throwing out the result.

Summary of Changes

• We've gone 2 years without this code throwing if the result is false or otherwise making use of the result. Let's just get rid of it?

Fixes #24822.

[codecov]

Codecov Report

Merging #25302 (9664194) into master (69a0ff9) will decrease coverage by 7.0%.
The diff coverage is n/a.

❗ Current head 9664194 differs from pull request most recent head 94b20b6. Consider uploading reports for the commit 94b20b6 to get more accurate results

@@             Coverage Diff             @@
##           master   #25302       +/-   ##
===========================================
- Coverage    82.0%    75.0%     -7.1%     
===========================================
  Files         598       38      -560     
  Lines      165882     2301   -163581     
  Branches        0      335      +335     
===========================================
- Hits       136125     1726   -134399     
+ Misses      29757      459    -29298     
- Partials        0      116      +116     

[jstarry]

Yeah, not sure why this was added, thanks for the cleanup!