Build failure due to proc_macro::Literal not impl from_str

[mattico]

In case anyone else runs into this:

error[E0599]: no function or associated item named `from_str` found for struct `proc_macro::Literal` in the current scope
   --> C:\Users\matth\.cargo\registry\src\github.com-1ecc6299db9ec823\proc-macro2-1.0.29\src\wrapper.rs:926:38
    |
926 |                 proc_macro::Literal::from_str(repr)
    |                                      ^^^^^^^^ function or associated item not found in `proc_macro::Literal`

error: aborting due to previous error

It was caused by using rustc 1.54.0-nightly (f94942d84 2021-05-19) which was from before rust-lang/rust#84717 was merged. Update your rustc.