Rollup merge of #142980 - shepmaster:mismatched-syntaxes-multi-suggestions, r=ehuss

Reduce mismatched-lifetime-syntaxes suggestions to MaybeIncorrect

`cargo fix` does not have a way of distinguishing a suggestion with
multiple spans which should all be applied from multiple suggestions
where only one should be applied (see rust-lang/rust#53934). `cargo fix` only works
with `MachineApplicable` suggestions, so downgrading the applicability
will stop `cargo` from suggesting the user run `cargo
fix`. rust-analyzer does work with `MaybeIncorrect`, so interactive
fixes are still available.

r? `@ehuss`

Author: workingjubilee