Update tests/ui/macros/expr_2021_with_metavar_expr.rs

Author: eholk

tests/ui/macros/expr_2021_with_metavar_expr.rs

@@ -2,7 +2,8 @@
 //@ aux-build: metavar_2021.rs
 //@ run-pass
 
-// This test captures the behavior of macro-generating-macros with fragment specifiers across edition b
+// This test captures the behavior of macro-generating-macros with fragment
+// specifiers across edition boundaries.
 
 #![feature(expr_fragment_specifier_2024)]
 #![feature(macro_metavar_expr)]