fix: do not enable testing feature in stacks-common

This can't be enabled outside of tests because it changes some default
values specifically for testing purposes.

stacks-signer/Cargo.toml

@@ -36,7 +36,7 @@ serde_stacker = "0.1"
 slog = { version = "2.5.2", features = [ "max_level_trace" ] }
 slog-json = { version = "2.3.0", optional = true }
 slog-term = "2.6.0"
-stacks-common = { path = "../stacks-common", features = ["testing"] }
+stacks-common = { path = "../stacks-common" }
 stackslib = { path = "../stackslib" }
 thiserror = { workspace = true }
 tiny_http = { version = "0.12", optional = true }