Update posts/2022-01-20-Rust-1.58.1.md

Author: pietroalbini

posts/2022-01-20-Rust-1.58.1.md

@@ -38,7 +38,7 @@ Rust 1.58.1 also addresses several regressions in diagnostics and tooling introd
   identifiers in format strings, introduced in Rust 1.58.0.
 * A regression in Rustfmt preventing generated files from being formatted when
   passed through the standard input has been fixed.
-* An incorrect error message displayed by `rustc` in some cases have been fixed.
+* An incorrect error message displayed by `rustc` in some cases has been fixed.
 
 You can find more detailed information on the specific regressions in the
 [release notes].