Remove LCOV exclusions for lines that could theoretically be taken

[mborland]

Closes: #1198

[codecov]

Codecov Report

❌ Patch coverage is 9.52381% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.8%. Comparing base (ae9076b) to head (c231a71).
⚠️ Report is 4 commits behind head on develop.

Files with missing lines	Patch %	Lines
include/boost/decimal/charconv.hpp	8.4%	11 Missing ⚠️
include/boost/decimal/detail/cmath/tgamma.hpp	0.0%	2 Missing ⚠️
include/boost/decimal/detail/io.hpp	0.0%	2 Missing ⚠️
include/boost/decimal/cstdlib.hpp	50.0%	1 Missing ⚠️
include/boost/decimal/detail/cmath/atan.hpp	0.0%	1 Missing ⚠️
include/boost/decimal/detail/fenv_rounding.hpp	0.0%	1 Missing ⚠️
include/boost/decimal/dpd_conversion.hpp	0.0%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #1248     +/-   ##
=========================================
- Coverage     99.1%   98.8%   -0.2%     
=========================================
  Files          264     264             
  Lines        17251   17296     +45     
  Branches      1931    1931             
=========================================
+ Hits         17079   17080      +1     
- Misses         172     216     +44     

Files with missing lines	Coverage Δ
include/boost/decimal/cstdio.hpp	97.6% <ø> (-2.4%)	⬇️
.../decimal/detail/fast_float/compute_float80_128.hpp	97.2% <ø> (-2.8%)	⬇️
include/boost/decimal/detail/parser.hpp	90.6% <ø> (-5.6%)	⬇️
include/boost/decimal/detail/to_float.hpp	90.0% <ø> (-10.0%)	⬇️
include/boost/decimal/cstdlib.hpp	92.1% <50.0%> (-7.9%)	⬇️
include/boost/decimal/detail/cmath/atan.hpp	96.5% <0.0%> (-3.5%)	⬇️
include/boost/decimal/detail/fenv_rounding.hpp	96.4% <0.0%> (-1.7%)	⬇️
include/boost/decimal/dpd_conversion.hpp	99.2% <0.0%> (-0.8%)	⬇️
include/boost/decimal/detail/cmath/tgamma.hpp	92.9% <0.0%> (-7.1%)	⬇️
include/boost/decimal/detail/io.hpp	85.4% <0.0%> (-14.6%)	⬇️
... and 1 more

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