Update syntax in create_tweet.rb

[icwizardmonke]

Kernel#gets is not a method to read from stdin.

Use $stdin.gets instead

gets reads from argument input

Screenshot shows the current code fails to run because gets tries to parse argument input ARGV

Change to $stdin.gets solves this problem

[github-actions[bot]]

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[icwizardmonke]

I have read the CLA Document and I hereby sign the CLA