These macros were replaced by __cpp_lib_map_try_emplace and
__cpp_lib_unordered_map_try_emplace, because those names are more
descriptive. We've kept both old and new names so far, but I think we
can remove the old ones now.
* include/bits/stl_map.h (__cpp_lib_map_insertion): Remove old
macro.
* include/bits/unordered_map.h (__cpp_lib_unordered_map_insertion):
Likewise.
* include/std/version (__cpp_lib_map_insertion)
(__cpp_lib_unordered_map_insertion): Remove.
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