Visual Studio 16.8 has different floating point precision

[tautschnig]

GitHub action runners now feature Visual Studio 16.8.1 (previously:
16.7). According to its STL changelog, this update includes the
following change:

microsoft/STL#1173 (review)

Therefore update the unit test to expect 13 trailing zeros.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #5613 (967383c) into develop (299307b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #5613   +/-   ##
========================================
  Coverage    69.33%   69.33%           
========================================
  Files         1241     1241           
  Lines       100424   100424           
========================================
  Hits         69625    69625           
  Misses       30799    30799           

Flag	Coverage Δ
cproversmt2	43.09% <ø> (ø)
regression	66.23% <ø> (ø)
unit	32.27% <ø> (ø)

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[martin-cs]

Changes like this make me despair for any kind of repeatable or cross-platform floating-point behaviour.