package/boost: bump to version 1.74.0 to fix C++20

package/boost: bump to version 1.74.0 to fix C++20

GCC 10 with -std=c++20 breaks boost library due to allocator changes.
https://github.com/boostorg/bimap/issues/23

We need boost 1.74.0 to fix build with gcc-10 -std=c++20. Note that none
of the Buildroot packages that use boost set -std=c++20, so no in-tree
failures.

Signed-off-by: Maxim Kochetkov <fido_max@inbox.ru>
Reviewed-by: Michael Nosthoff <buildroot@heine.tech>
Tested-by: Michael Nosthoff <buildroot@heine.tech>  for arm
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>