Drop setting a default value for DEPLOY_PRIME_URL

Author: chalin

Makefile

@@ -1,7 +1,6 @@
 HUGO_VERSION      = $(shell grep ^HUGO_VERSION netlify.toml | tail -n 1 | cut -d '=' -f 2 | tr -d " \"\n")
 NODE_BIN          = node_modules/.bin
 NETLIFY_FUNC      = $(NODE_BIN)/netlify-lambda
-DEPLOY_PRIME_URL ?=/
 
 # The CONTAINER_ENGINE variable is used for specifying the container engine. By default 'docker' is used
 # but this can be overridden when calling make, e.g.