[Rust] Format example with rustfmt

[euank]

This was handled via 'cargo fmt' on the current nightly rust. I also
moved a few lines around and deleted an old comment.

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Description of the PR

Since #7335 merged, this updates the example to match that style in the sample example.

I'll go through and update the style in more places once I don't have other PRs which would merge-conflict in flight.

cc @frol @farcaller @bjgill

[frol]

LGTM

[bjgill]

Nice. Do you not need to update the mustache template that generates this, instead, though?

[euank]

@bjgill the 'examples' folder isn't generated from mustache templates; it only lives in that location as far as I can tell.

I would like to update the moustache template's style too, but I'm trying to avoid merge conflicts by doing that after the other in-flight PRs I have land.

[wing328]

@euank thanks for the PR, which has been merged into 2.4.0.

What about running "cargo fmt" automatically in the output folder after generating the Rust code?

[euank]

@wing328 I like that idea, but I assumed that depending on cargo would be an issue. I noticed that the go generated client doesn't meet gofmt standards and gofmt isn't automatically run, so I sorta assumed rust shouldn't be calling tools like that either.

[wing328]

@euank I've some ideas. Will try to implement one later and collect feedback from you guys.