Suppress superfluous debug string in mctest

[willend]

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Please describe what your PR is adding in terms of features or bugfixes:

mctest output was previously:

Compiling instruments [seconds]...
PSI_DMC        :   4.74
PSI_DMC_simple :   4.24

Running tests / getting status...
%-16s:   3.99
PSI_DMC         :   3.99    [val: 832.142 / 759.65 = 110 %]
%-16s:   2.36
PSI_DMC_simple  :   2.36    [val: 876.968 / 759.65 = 115 %]

Now corrected to become:

Compiling instruments [seconds]...
PSI_DMC        :   4.52
PSI_DMC_simple :   4.12

Running tests / getting status...
PSI_DMC         :   3.27    [val: 832.142 / 759.65 = 110 %]
PSI_DMC_simple  :   2.20    [val: 876.968 / 759.65 = 115 %]
======================================
Overall test result:
SUCCESS

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Development OS / boundary conditions

Please describe what OS you developed and tested your additions on, and if any special dependencies are required:

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PR Checklist for contributing to McStas/McXtrace

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• My contribution includes patches to an existing component file

  • I have used the mcdoc utility and rendered a reasonable documentation page for the component (please attach as screenshot in comments!)
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  • I have used the mcrun --c-lint "linter" and followed advice to remove most / all warnings that are raised

• My contribution includes patches to an existing instrument file

  • I have used the mcdoc utility and rendered a reasonable documentation page for the instrument (please attach as screenshot in comments!)
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  • I have used the mcrun --c-lint "linter" and followed advice to remove most / all warnings that are raised

• My contribution includes a new component file

  • I have ensured that naming of parameters are in the style of existing components. (Please check the McStas or McXtrace NOMENCLATURE docs.)
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  • I have used the mcdoc utility and rendered a reasonable documentation page for the component (please attach as screenshot in comments!)
  • I have ensured that basic use of the component is OK (e.g. an instrument using it compiles?)
  • I have included a corresponding example instrument and will fill in the new instrument section below
  • My new component is added within the contrib component category

• My contribution includes a new instrument file

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  • I have ensured that basic use of the instrument is OK (e.g. it compiles?)
  • ... and provided reasonable default parameters in that instrument that produce reasonable output
  • ... and maybe even added a %Example: line to describe expected behaviour
  • I have used the mcrun --c-lint "linter" and followed advice to remove most / all warnings that are raised
  • My new instrument is added within the examples hierarchy in a folder in the style of examples/ESS/New_stuff/New_stuff.instr
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• My work touches the code-generator in mccode/src

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  • I am attaching test output in the comments

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• My PR is meant to fix a specific, existing issue

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• My contribution contains something else

  • Explanation is added in free form text above or below the checklist

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