relay-builder: enable std feature for base64

Signed-off-by: Yuki Kishimoto <[email protected]>

Author: yukibtc

crates/nostr-relay-builder/Cargo.toml

@@ -26,7 +26,7 @@ tokio = { workspace = true, features = ["macros", "net", "sync"] }
 tracing.workspace = true
 
 [dev-dependencies]
-base64.workspace = true
+base64 = { workspace = true, features = ["std"] }
 hyper = { version = "1.6", features = ["server", "http1"] }
 hyper-util = { version = "0.1", features = ["tokio"] }
 tracing-subscriber = { workspace = true, features = ["env-filter"] }