core.policies should be core:policies in dependencies.rst

[YuZhen-Yang]

In reference/binary_model/dependencies.rst, the global.conf example uses an incorrect key name:

core.policies=["required_conan_version>=2.28"]

It should be:

core:policies=["required_conan_version>=2.28"]

Using core.policies causes the following error at runtime:

Error in Conan initialization: [conf] 'core.policies' does not exist in configuration list.

File: reference/binary_model/dependencies.rst, line 56
Branch: release/2.28

[memsharded]

Hi @YuZhen-Yang

Thanks for pointing this. Yes, this looks like a typo, lets fix it.

[memsharded]

Closed by #4453, thanks!