Bump proc-macro-warning from 0.4.1 to 0.4.2 (paritytech#1376)

Bumps [proc-macro-warning](https://github.com/ggwpez/proc-macro-warning) from 0.4.1 to 0.4.2.
- [Release notes](https://github.com/ggwpez/proc-macro-warning/releases)
- [Commits](ggwpez/proc-macro-warning@v0.4.1...v0.4.2)

---
updated-dependencies:
- dependency-name: proc-macro-warning
  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>

substrate/frame/support/procedural/Cargo.toml

@@ -23,7 +23,7 @@ proc-macro2 = "1.0.56"
 quote = "1.0.28"
 syn = { version = "2.0.16", features = ["full"] }
 frame-support-procedural-tools = { path = "tools" }
-proc-macro-warning = { version = "0.4.1", default-features = false }
+proc-macro-warning = { version = "0.4.2", default-features = false }
 macro_magic = { version = "0.4.2", features = ["proc_support"] }
 expander = "2.0.0"