remove the build.release task. Use shards build instead.

[jwoertink]

Purpose

Fixes #1564
Closes #1593

Description

Originally this task ran the crystal build --release ./src/start_server.cr -o ./bin/start_server command for you. That was a really long command to run, so running lucky build.release was a lot easier to remember.

I wanted to just update this task to use shards build instead because if you have more than 1 binary for your app (i.e. workers, etc...), then this task wouldn't really work anyway. In fact, the heroku buildpack doesn't use it either for that reason.

I ended up deciding to just remove it because when I started updating it, I realized I would want to print which binaries were built, and that required parsing YAML. Then there was a spec file which wouldn't work without creating a whole temp project. Really in the end, shards build --production --release is pretty short, and more flexible.

Checklist

• - An issue already exists detailing the issue/or feature request that this PR fixes
• - All specs are formatted with crystal tool format spec src
• - Inline documentation has been added and/or updated
• - Lucky builds on docker with ./script/setup
• - All builds and specs pass on docker with ./script/test