"[TRIVIAL] Set version to 2.5.0-b1".

[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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.3%. Comparing base (380ba9f) to head (09690f1).
Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #5433   +/-   ##
=======================================
  Coverage     78.2%   78.3%           
=======================================
  Files          800     800           
  Lines        69025   69027    +2     
  Branches      8299    8278   -21     
=======================================
+ Hits         53986   54019   +33     
+ Misses       15039   15008   -31     

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

... and 8 files with indirect coverage changes

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