updates attenuation info output

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 62.50000% with 54 lines in your changes missing coverage. Please review.

Project coverage is 53.25%. Comparing base (a2b578f) to head (e98495b). Report is 2 commits behind head on devel.

Files with missing lines	Patch %	Lines
src/specfem2D/prepare_attenuation.f90	62.50%	54 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## devel #1243 +/- ## ========================================== + Coverage 53.20% 53.25% +0.04% ========================================== Files 171 171 Lines 31412 31452 +40 ========================================== + Hits 16714 16749 +35 - Misses 14698 14703 +5 ``` | [Flag](https://app.codecov.io/gh/SPECFEM/specfem2d/pull/1243/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SPECFEM) | Coverage Δ | | |---|---|---| | [](https://app.codecov.io/gh/SPECFEM/specfem2d/pull/1243/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SPECFEM) | `53.25% <62.50%> (?)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SPECFEM#carryforward-flags-in-the-pull-request-comment) to find out more.

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