mintd: remove non-existent stdout logging from docs (#1159)

crates/cdk-mintd/example.config.toml

@@ -14,8 +14,7 @@ melt_ttl = 120
 
 
 [info.logging]
-# Where to output logs: "stdout", "file", or "both" (default: "both")
-# Note: "stdout" actually outputs to stderr (standard error stream)
+# Where to output logs: "stderr" (standard error stream), "file", or "both" (default: "both")
 # output = "both"
 # Log level for console output (default: "info")
 # console_level = "info"