chore: fix missing space in the hint for errorsn.rs

Author: avrong

info.toml

@@ -501,7 +501,7 @@ mode = "test"
 hint = """
 First hint: To figure out what type should go where the ??? is, take a look
 at the test helper function `test_with_str`, since it returns whatever
-`read_and_validate` returns and`test_with_str` has its signature fully
+`read_and_validate` returns and `test_with_str` has its signature fully
 specified.