Upgrade guzzlehttp/guzzle

[nikeee]

• I was not able to find an open or closed issue matching what I'm seeing.
• This is not a question.

For my current project, we depend on guzzlehttp/guzzle ^7. According to their docs, guzzle 7 requires PHP > 7.2.5, which aligns pretty closely with this project's target >= 7.2.