Fix typo in trace validation script

[thk123]

The only useful work from this branch is fixing one typo - but hey, might as well.

• Each commit message has a non-empty body, explaining why the change was made.
• Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• [na] The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• [na] 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).
• [na] My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
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[thk123]

Looks like the two failing jobs that need to turn this off are:

• (cbmc-linux-cmake-gcc)
• (cbmc-windows)

I realise now that it is going to be hard to disable the tests for make which makes me sad - so probably the make ones will have to spuriously pass, but make the cmake one at least be safe (and use -E to exclude the xsd tests)

[thk123]

cbmc-linux-cmake-gcc: missing xml-line:

xmllint not found, trace schema tests will fail 

cbmc-windows:

python3 not found: traces not validated against XSD 

Last failure (cbmc-windows-cmake) looks spurious so have hit retry

[codecov-io]

Codecov Report

Merging #5315 into develop will decrease coverage by 36.18%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           develop    #5315       +/-   ##
============================================
- Coverage    67.95%   31.76%   -36.19%     
============================================
  Files         1170      918      -252     
  Lines        96362    80168    -16194     
============================================
- Hits         65478    25465    -40013     
- Misses       30884    54703    +23819     

Flag	Coverage Δ
#cproversmt2	?
#regression	?
#unit	31.76% <ø> (ø)

Impacted Files	Coverage Δ
src/cpp/cpp_id.h	0.00% <0.00%> (-100.00%)	⬇️
src/cpp/cpp_scope.h	0.00% <0.00%> (-100.00%)	⬇️
src/cpp/cpp_token.h	0.00% <0.00%> (-100.00%)	⬇️
src/cpp/cpp_name.cpp	0.00% <0.00%> (-100.00%)	⬇️
src/cpp/cpp_util.cpp	0.00% <0.00%> (-100.00%)	⬇️
src/util/identifier.h	0.00% <0.00%> (-100.00%)	⬇️
src/xmllang/graphml.h	0.00% <0.00%> (-100.00%)	⬇️
src/cpp/cpp_is_pod.cpp	0.00% <0.00%> (-100.00%)	⬇️
src/cpp/template_map.h	0.00% <0.00%> (-100.00%)	⬇️
src/ansi-c/designator.h	0.00% <0.00%> (-100.00%)	⬇️
... and 893 more

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[hannes-steffenhagen-diffblue]

I think this PR should have a less scary name.