Bump proc-macro2 from 1.0.54 to 1.0.56 (#406)

Bumps [proc-macro2](https://github.com/dtolnay/proc-macro2) from 1.0.54 to 1.0.56.
- [Release notes](https://github.com/dtolnay/proc-macro2/releases)
- [Commits](https://github.com/dtolnay/proc-macro2/compare/1.0.54...1.0.56)

---
updated-dependencies:
- dependency-name: proc-macro2
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.lock

@@ -1167,9 +1167,9 @@ checksum = "eb9f9e6e233e5c4a35559a617bf40a4ec447db2e84c20b55a6f83167b7e57872"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.54"
+version = "1.0.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e472a104799c74b514a57226160104aa483546de37e839ec50e3c2e41dd87534"
+checksum = "2b63bdb0cd06f1f4dedf69b254734f9b45af66e4a031e42a7480257d9898b435"
 dependencies = [
  "unicode-ident",
 ]