doc/api.rst: remove reference to `miniswift` mod
doc/api.rst: remove reference to `miniswift` mod

This module has been removed, and the doc build was displaying a warning
about the missing module.

zerovm/zpm,zerovm/zpm,zerovm/zpm,zerovm/zerovm-cli,zerovm/zpm,zerovm/zpm,zerovm/zpm,zerovm/zerovm-cli,zerovm/zerovm-cli,zerovm/zerovm-cli,zerovm/zerovm-cli,zerovm/zerovm-cli