fix(mfsfr2.check): make "reach_connection_gaps.chk.csv" a normal CSV file

[mwtoews]

While the previous format of "reach_connection_gaps.chk.csv" was a text file, it was not well formatted.

This PR writes the numpy recarray as a conventional CSV file.

[mwtoews]

On further inspection, the purpose of this file is not clear. It simply an output of reach_data. It does not appear to contain any information on reach connection gaps. I suggest this output file to be removed.

[codecov]

Codecov Report

Merging #1151 (5eb573c) into develop (b780bfb) will increase coverage by 1.578%.
The diff coverage is 100.000%.

❗ Current head 5eb573c differs from pull request most recent head 948d79c. Consider uploading reports for the commit 948d79c to get more accurate results

@@              Coverage Diff              @@
##           develop     #1151       +/-   ##
=============================================
+ Coverage   72.291%   73.869%   +1.578%     
=============================================
  Files          227       227               
  Lines        52640     51518     -1122     
=============================================
+ Hits         38054     38056        +2     
+ Misses       14586     13462     -1124     

Impacted Files	Coverage Δ
flopy/modflow/mfsfr2.py	88.085% <100.000%> (+0.016%)	⬆️
flopy/mf6/modflow/__init__.py	100.000% <0.000%> (+4.838%)	⬆️
flopy/mf6/modflow/mfgnc.py	52.941% <0.000%> (+20.798%)	⬆️
flopy/mf6/modflow/mfmvr.py	52.380% <0.000%> (+20.952%)	⬆️
flopy/mf6/modflow/mfgwtdisu.py	47.500% <0.000%> (+23.449%)	⬆️
flopy/mf6/modflow/mfgwt.py	57.142% <0.000%> (+25.142%)	⬆️
flopy/mf6/modflow/mfgwfgwt.py	100.000% <0.000%> (+27.777%)	⬆️
flopy/mf6/modflow/mfgwtadv.py	100.000% <0.000%> (+28.571%)	⬆️
flopy/mf6/modflow/mfgwfic.py	100.000% <0.000%> (+33.333%)	⬆️
flopy/mf6/modflow/mfgwtic.py	100.000% <0.000%> (+33.333%)	⬆️
... and 50 more