Don't explicitly warn against semicolon_in_expressions_from_macros

This has been warn-by-default for two years now and has already been
added to the future-incompat lints in 1.68.

crates/stdx/src/lib.rs

@@ -1,6 +1,6 @@
 //! Missing batteries for standard libraries.
 
-#![warn(rust_2018_idioms, unused_lifetimes, semicolon_in_expressions_from_macros)]
+#![warn(rust_2018_idioms, unused_lifetimes)]
 
 use std::io as sio;
 use std::process::Command;