Remove 'apostrophes' from rustc_parse_format

[ShE3py]

The rest of the compiler uses `grave accents`, while rustc_parse_format uses `'apostrophes.'`

Also makes the crate compile as a stand-alone:

~/rust/compiler/rustc_parse_format $ cargo check
   Compiling rustc_index_macros v0.0.0 (/home/lieselotte/rust/compiler/rustc_index_macros)
error[E0277]: `syn::Lit` doesn't implement `Debug`
  --> compiler/rustc_index_macros/src/newtype.rs:52:57
   |
52 |                         panic!("Specified multiple max: {old:?}");
   |                                                         ^^^^^^^ `syn::Lit` cannot be formatted using `{:?}` because it doesn't implement `Debug`
   |
   = help: the trait `Debug` is not implemented for `syn::Lit`
   = note: this error originates in the macro `$crate::const_format_args` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: `syn::Lit` doesn't implement `Debug`
  --> compiler/rustc_index_macros/src/newtype.rs:64:74
   |
64 |                         panic!("Specified multiple debug format options: {old:?}");
   |                                                                          ^^^^^^^ `syn::Lit` cannot be formatted using `{:?}` because it doesn't implement `Debug`
   |
   = help: the trait `Debug` is not implemented for `syn::Lit`
   = note: this error originates in the macro `$crate::const_format_args` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0277`.
error: could not compile `rustc_index_macros` (lib) due to 2 previous errors

@rustbot label +A-diagnostics

[rustbot]

r? @nnethercote

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[compiler-errors]

r? compiler-errors @bors r+

[bors]

📌 Commit dda3066 has been approved by compiler-errors

It is now in the queue for this repository.