Fix deprecated whitespace in literal definition

[mborland]

Warning was emitted by Clang-20

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.7%. Comparing base (b9adb39) to head (c825582).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop    #771     +/-   ##
=========================================
+ Coverage     98.7%   98.7%   +0.1%     
=========================================
  Files          223     223             
  Lines        16728   16728             
  Branches      1796    1796             
=========================================
+ Hits         16503   16505      +2     
+ Misses         225     223      -2     

Files with missing lines	Coverage Δ
include/boost/decimal/literals.hpp	100.0% <100.0%> (ø)

... and 1 file with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b9adb39...c825582. Read the comment docs.