doc: add minimum required kernel version to dependencies.md

This matches the version of the kernel targeted when we build the glibcs
we use for release builds in Guix. Other versions / scenerios may
work, but for documentation purposes, this is the version that makes
sense to document, and something we can claim to officially support.

doc/dependencies.md

@@ -20,6 +20,7 @@ You can find installation instructions in the `build-*.md` file for your platfor
 | [Boost](../depends/packages/boost.mk) | [link](https://www.boost.org/users/download/) | [1.77.0](https://github.com/bitcoin/bitcoin/pull/24383) | [1.64.0](https://github.com/bitcoin/bitcoin/pull/22320) | No |
 | [libevent](../depends/packages/libevent.mk) | [link](https://github.com/libevent/libevent/releases) | [2.1.12-stable](https://github.com/bitcoin/bitcoin/pull/21991) | [2.1.8](https://github.com/bitcoin/bitcoin/pull/24681) | No |
 | glibc | [link](https://www.gnu.org/software/libc/) | N/A | [2.18](https://github.com/bitcoin/bitcoin/pull/23511) | Yes |
+| Linux Kernel | [link](https://www.kernel.org/) | N/A | 3.2.0 | Yes |
 
 ## Optional