math/wxmaxima: Remove obsolete patch

[salvadore]

Summary

According to the 20200115 entry of CHANGES, man pages can (and should) now be installed in ${PREFIX}/share/man. This makes obsolete math/wxmaxima/files/patch-data_CMakeLists.txt.

While here, I also fixed sorting in pkg-plist.

[gerald]

Yep, thank you.

A minor language suggestion:
"This makes obsolete X" -> "This makes X obsolete" *or* "This obsoletes X" - I'd probably go for the latter.