Remove deprecated variant of parse_unwindset

[tautschnig]

The remaining use of the deprecated variant was updated accordingly.

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• 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).
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[codecov]

Codecov Report

Merging #5565 (4961f2d) into develop (aa069d3) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #5565   +/-   ##
========================================
  Coverage    69.31%   69.31%           
========================================
  Files         1241     1241           
  Lines       100407   100407           
========================================
  Hits         69596    69596           
  Misses       30811    30811           

Flag	Coverage Δ
cproversmt2	43.07% <50.00%> (-0.01%)	⬇️
regression	66.21% <100.00%> (ø)
unit	32.27% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/goto-instrument/unwindset.h	100.00% <ø> (ø)
src/goto-instrument/unwindset.cpp	85.29% <100.00%> (ø)

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