A11y: export gtk_cell_accessible_parent_get_(row|column)_header_cells

These functions were missing GDK_AVAILABLE_IN macros, so they were
listed in the gir but not exported.
2 jobs from gtk-3-24 in 7 minutes and 47 seconds
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passed #186066
build

00:07:47

manual #186067
win32 allowed to fail manual
msys2-mingw32