[TRIVIAL] Set version to 2.5.0-b2

[legleux]

High Level Overview of Change

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

[legleux]

Making rc1

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.0%. Comparing base (a5e953b) to head (5f51e02).

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #5471     +/-   ##
=========================================
- Coverage     79.0%   79.0%   -0.0%     
=========================================
  Files          817     817             
  Lines        71738   71738             
  Branches      8287    8293      +6     
=========================================
- Hits         56690   56679     -11     
- Misses       15048   15059     +11     

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

... and 5 files with indirect coverage changes

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