Remove obsolete docker build

Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>

sample-functions/ApiKeyProtected/Dockerfile.build

-FROM golang:1.7.5
-RUN mkdir -p /go/src/app
-COPY handler.go /go/src/app
-WORKDIR /go/src/app
-
-RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o app .
-
-CMD ["echo"]
-

sample-functions/ApiKeyProtected/build.sh

-#!/bin/sh
-echo Building functions/api-key-protected:build
-
-docker build --build-arg https_proxy=$https_proxy --build-arg http_proxy=$http_proxy \
-    -t functions/api-key-protected . -f Dockerfile.build
-
-docker create --name render_extract functions/api-key-protected
-docker cp render_extract:/go/src/app/app ./app
-docker rm -f render_extract
-
-echo Building functions/api-key-protected:latest
-docker build --no-cache -t functions/api-key-protected:latest .