fix: Make RequestValidator#validate fail if URL has no query params

[haffla]

Fixes #613

I ran into this issue when I wrongly expected JSON requests I am making from a Twilio serverless function to one of my services to be correctly verified. I know that Twilio will always include the bodySHA256 query parameter for JSON requests. But if you use Twilio::Security::RequestValidator#validate in a custom way you might pass the wrong URL and in that case it shouldn't crash.

Checklist

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