Proposal: Rename tag C-good first issue to good first issue

[Xuanwo]

Github has native good first issue support which makes the good first issue label special.

For example

https://github.com/datafuselabs/opendal/contribute

Compared to

https://github.com/datafuselabs/databend/contribute

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Resolved

[Xuanwo]

Ping @BohuTANG for review.

[TCeason]

Maybe we also can add our contribution in the future.

https://databend.rs/doc/contributing