Add hd111980_stis_006.fits to test cache.

[erykoff]

At some point getcalspec was updated and a new filename for the test spectrum was returned. This meant that spectractor had to touch the internet and stsci servers to run tests, which is not 100% reliable.

This PR adds the 006 spectrum to the test cache.

It would also be nice if one could specify to getcalspec a version of a spectrum (rather than just the most recent) but that's another larger issue.

[coveralls]

Pull Request Test Coverage Report for Build 8683266377

Details

• 3 of 3 (100.0%) changed or added relevant lines in 2 files are covered.
• 1483 unchanged lines in 20 files lost coverage.
• Overall coverage decreased (-16.2%) to 71.556%

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Files with Coverage Reduction	New Missed Lines	%
spectractor/simulation/atmosphere.py	1	95.36%
spectractor/config.py	1	86.32%
spectractor/fit/fit_spectrogram.py	1	93.96%
spectractor/fit/fit_multispectra.py	3	83.7%
spectractor/simulation/libradtran.py	3	68.0%
spectractor/logbook.py	15	64.52%
spectractor/astrometry.py	20	39.29%
spectractor/simulation/throughput.py	25	63.41%
spectractor/extractor/targets.py	31	54.44%
spectractor/extractor/extractor.py	35	83.15%

Totals
Change from base Build 7275666541:	-16.2%
Covered Lines:	5761
Relevant Lines:	8051

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💛 - Coveralls