Fix reference to validate_bool in function
Fix reference to validate_bool in function

The documentation in `validate_ip_address` references `validate_bool`,
but I believe this should read `validate_ip_address` instead, which
makes more sense.

Looks like this was copied from `validate_ipv4_address`, which I fixed
in 7b068781.

puppetlabs/puppetlabs-stdlib,fuel-infra/puppetlabs-stdlib,jbondpdx/puppetlabs-stdlib,yadavnikhil/puppetlabs-stdlib,HelenCampbell/puppetlabs-stdlib,DavidS/puppetlabs-stdlib