Fix duplicated GPU annotations

[mborland]

Found investigating #1357

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.32%. Comparing base (a377d2c) to head (a24711a).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1358   +/-   ##
========================================
  Coverage    95.32%   95.32%           
========================================
  Files          825      825           
  Lines        67994    67994           
========================================
+ Hits         64814    64815    +1     
+ Misses        3180     3179    -1     

Files with missing lines	Coverage Δ
include/boost/math/tools/rational.hpp	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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