doc(mf6io): netcdf documentation fixes (#2207) #3929

Job	Run time
Smoke test	8m 51s
Check format	1m 13s
Build	5m 47s
Extended testing (ubuntu-22.04)	24m 11s
Extended testing (macos-13)	46m 49s
Test Intel fortran (ubuntu-22.04)	39m 9s
Extended testing (windows-2022)	52m 36s
Test GNU fortran (macos-13, false)	40m 54s
Test Intel fortran (macos-13)	31m 15s
Test GNU fortran (macos-14, false)	37m 10s
Test Intel fortran (windows-2022)	34m 21s
Test GNU fortran (macos-14, true)	1h 12m 2s
Test GNU fortran (ubuntu-22.04, false)	43m 38s
Test GNU fortran (ubuntu-22.04, true)	1h 36m 6s
Test GNU fortran (windows-2022, false)	52m 36s
	9h 46m 38s

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