fix(mf6io): cleanup description of EVAPORATION keyword in SFE and LKE #3621

Job	Run time
Smoke test	5m 46s
Build	1m 44s
Check format	1m 56s
Extended testing (ubuntu-22.04)	18m 9s
Test Intel fortran (ubuntu-22.04)	41m 3s
Extended testing (macos-13)	45m 33s
Test GNU fortran (macos-13, false)	24m 41s
Test Intel fortran (macos-13)	24m 42s
Test GNU fortran (macos-14, false)	21m 52s
Extended testing (windows-2022)	55m 26s
Test Intel fortran (windows-2022)	36m 57s
Test GNU fortran (macos-14, true)	37m 54s
Test GNU fortran (ubuntu-22.04, false)	39m 4s
Test GNU fortran (ubuntu-22.04, true)	1h 31m 28s
Test GNU fortran (windows-2022, false)	33m 27s
	7h 59m 42s

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