Install wx/osx/appprogress as part of "make install"

Add the file to the files list, this should have been part of
11a5b83e2c (see #16638).

Closes #18059.

build/cmake/files.cmake

@@ -2280,6 +2280,7 @@ set(OSX_SHARED_HDR
     wx/generic/listctrl.h
     wx/generic/prntdlgg.h
     wx/generic/statusbr.h
+    wx/osx/appprogress.h
 )
 
 set(OSX_COCOA_SRC