Mark external/boost/c++20-allocator.patch.0 as partially covered upstream

Change-Id: I086e51c581202cd8c68a5a408b8d7575c953461d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/91347
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>
diff --git a/external/boost/UnpackedTarball_boost.mk b/external/boost/UnpackedTarball_boost.mk
index acb6d6a..046f7e6 100644
--- a/external/boost/UnpackedTarball_boost.mk
+++ b/external/boost/UnpackedTarball_boost.mk
@@ -37,6 +37,8 @@ boost_patches += gcc9.patch.0

boost_patches += msvc2017.patch.0

# boost/format/alt_sstream_impl.hpp part covered by <https://github.com/boostorg/format/pull/70>
# "Removed deprecated std::allocator<void>":
boost_patches += c++20-allocator.patch.0

$(eval $(call gb_UnpackedTarball_UnpackedTarball,boost))