Upgrade proc-macro-crate to 3.4.0 in order fix compilation under bazel

rstest currently fails to build under bazel with
```
error: custom attribute panicked
    |
250 |     #[rstest]
    |     ^^^^^^^^^
    |
    = help: message: rstest is present in `Cargo.toml` qed: Could not find `Cargo.toml` in manifest dir:
```

I've tracked this back to proc-macro-crate, which fixed it in bkchr/proc-macro-crate#55

Author: rossdylan

rstest_macros/Cargo.toml

@@ -37,7 +37,7 @@ syn = { version = "2.0.79", features = [
     "visit-mut",
 ] }
 unicode-ident = "1.0.13"
-proc-macro-crate = { version = "3.2.0", optional = true }
+proc-macro-crate = { version = "3.4.0", optional = true }
 
 [dev-dependencies]
 maplit = "1.0.2"