Allow Sentry.init without block argument

[sue445]

Description

When SENTRY_DSN has been passed from environment variable, config.dsn in Sentry.init is needless.

But simply call Sentry.init will result in an error

e.g.

# example.rb
require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"
  gem "sentry-ruby", "4.1.4"
end

require "sentry-ruby"

Sentry.init

$ SENTRY_DSN=xxxxxx ruby example.rb

/Users/sue445/.rbenv/versions/3.0.0/lib/ruby/gems/3.0.0/gems/sentry-ruby-4.1.4/lib/sentry-ruby.rb:67:in `init': no block given (yield) (LocalJumpError)
	from example.rb:10:in `<main>'

The workaround is below, but it's a bit dirty...

Sentry.init do
  # nop
end

# or

Sentry.init {  }

So I made it possible to call Sentry.init without block

[st0012]

Thanks for the change 👍