Improve redundant_locals help message

[koka831]

Fixes #11625

AFAIK, span_lint_and_help points the beginning of spans when we pass multiple spans to the second argument, so This PR I also modified its help span and its message.

lint result of the given example in the issue will be:

error: redundant redefinition of a binding `apple`
 --> src/main.rs:5:5
  |
5 |     let apple = apple;
  |     ^^^^^^^^^^^^^^^^^^
  |
help: `apple` is initially defined here
 --> src/main.rs:4:9
  |
4 |     let apple = 42;
  |         ^^^^^
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#redundant_locals

I hope that this change might help reduce user confusion, but I'd appreciate alternative suggestions:)

changelog: [redundant_locals]: Now points at the rebinding of the variable

[rustbot]

r? @Jarcho

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[blyxyas]

You can use "Fixes #[issue number]" instead of "Addresses [URL]" to automatically close the original issue. (Documentation)

[blyxyas]

Smart implementation, thanks for addressing this issue ❤️!

[blyxyas]

@bors r+

[bors]

📌 Commit 48d2770 has been approved by blyxyas

It is now in the queue for this repository.

[bors]

⌛ Testing commit 48d2770 with merge 7217c0f...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: blyxyas
Pushing 7217c0f to master...