Use mir::SourceInfo again in FunctionCx.source_info_set

https://github.com/bjorn3/rustc_codegen_cranelift/blob/0219f218db666ed597d279d6258b31fc611ae42a/src/common.rs#L289

Changed to current state in https://github.com/bjorn3/rustc_codegen_cranelift/commit/853651430824b49ab1e995b6bdcf2705badb99b1 Not necessary since https://github.com/rust-lang/rust/pull/65828