[TRIVIAL] Set version to 2.4.0-b2

[ximinez]

High Level Overview of Change

This PR only changes the version number. It will be merged as
soon as Github CI actions successfully complete.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.0%. Comparing base (839d17e) to head (ebd8e63).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #5248   +/-   ##
=======================================
  Coverage     78.0%   78.0%           
=======================================
  Files          789     789           
  Lines        66955   66955           
  Branches      8110    8132   +22     
=======================================
+ Hits         52214   52223    +9     
+ Misses       14741   14732    -9     

Files with missing lines	Coverage Δ
src/libxrpl/protocol/BuildInfo.cpp	98.2% <ø> (ø)

... and 2 files with indirect coverage changes