Rollup merge of #64202 - alexreg:rush-pr-1, r=Centril

Fixed grammar/style in some error messages

Factored out from hacking on rustc for work on the REPL.

r? @Centril

src/libsyntax/parse/parser/expr.rs

@@ -982,7 +982,7 @@ impl<'a> Parser<'a> {
                 }
                 if self.is_do_catch_block() {
                     let mut db = self.fatal("found removed `do catch` syntax");
-                    db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
+                    db.help("following RFC #2388, the new non-placeholder syntax is `try`");
                     return Err(db);
                 }
                 if self.is_try_block() {