Update proc-macro-crate requirement from 2 to 3

Updates the requirements on [proc-macro-crate](https://github.com/bkchr/proc-macro-crate) to permit the latest version.
- [Release notes](https://github.com/bkchr/proc-macro-crate/releases)
- [Commits](bkchr/proc-macro-crate@v2.0.0...v3.0.0)

---
updated-dependencies:
- dependency-name: proc-macro-crate
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

gdnative-derive/Cargo.toml

@@ -18,7 +18,7 @@ proc-macro = true
 syn = { version = "1", features = ["full", "extra-traits", "visit"] }
 quote = "1"
 proc-macro2 = "1"
-proc-macro-crate = "2"
+proc-macro-crate = "3"
 
 [dev-dependencies]
 # This is included for the doc tests.