Bump proc-macro2 from 1.0.39 to 1.0.40

Bumps [proc-macro2](https://github.com/dtolnay/proc-macro2) from 1.0.39 to 1.0.40.
- [Release notes](https://github.com/dtolnay/proc-macro2/releases)
- [Commits](https://github.com/dtolnay/proc-macro2/compare/1.0.39...1.0.40)

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

Signed-off-by: dependabot[bot] <support@github.com>

pallets/parachain-system/proc-macro/Cargo.toml

@@ -10,7 +10,7 @@ proc-macro = true
 
 [dependencies]
 syn = "1.0.96"
-proc-macro2 = "1.0.39"
+proc-macro2 = "1.0.40"
 quote = "1.0.18"
 proc-macro-crate = "1.1.3"