chore: remove unused async-std dependency from c2patool (#1249)

Author: ok-nick

Cargo.lock

@@ -23,11 +23,11 @@ unexpected_cfgs = { level = "warn", check-cfg = ['cfg(test)'] }
 anyhow = "1.0"
 atree = "0.5.2"
 c2pa = { path = "../sdk", version = "0.58.0", features = [
-	"fetch_remote_manifests",
-	"file_io",
-	"add_thumbnails",
-	"pdf"
-]}
+    "fetch_remote_manifests",
+    "file_io",
+    "add_thumbnails",
+    "pdf",
+] }
 clap = { version = "4.5.10", features = ["derive", "env", "string"] }
 env_logger = "0.11.7"
 glob = "0.3.1"
@@ -43,7 +43,6 @@ url = "2.5.0"
 etcetera = "0.10.0"
 
 [target.'cfg(not(target_os = "wasi"))'.dependencies]
-async-std = { version = "1.12", features = ["attributes"] }
 reqwest = { version = "0.12.4", features = ["blocking"] }
 tokio = { version = "1.44.2", features = ["rt", "rt-multi-thread"] }