go directive in go.mod is unnecessarily specific

Description

The go directive sets the minimum version of Go required to use this module. There's no need to set this to the latest semver patch version of a given Go release unless the semantics of that version of Go are required to build/test/use the module.

Notably since PR #1865 any consumers of sigstore as a library would need to bump their own go directive to 1.22.8 in order to pickup the sigstore 1.8.10 release.