lint: clarify the need to update configlet (#504)

Before this commit, the message incorrectly implied that just re-running
`configlet lint` was sufficient to use the latest linting rules. Clarify
that the user must update configlet first.

src/lint/lint.nim

@@ -24,7 +24,8 @@ proc allChecksPass(trackDir: Path): bool =
 proc lint*(conf: Conf) =
   echo """
     The lint command is under development.
-    Please re-run this command regularly to see if your track passes the latest linting rules.
+    To check your track using the latest linting rules,
+    please regularly update configlet and re-run this command.
   """.unindent()
 
   let trackDir = Path(conf.trackDir)