lint: advise that warnings may not become errors (#490)

Before this commit, configlet advised that warnings in the
`configlet lint` output would definitely become errors in the future.

However, the website was updated to gracefully handle the cases that
configlet warned about. We may no longer want the warnings to become
errors, so let's communicate that.

src/lint/lint.nim

@@ -56,6 +56,6 @@ For more information on resolving the problems, please see the documentation:
     echo ""
     const msg = """
       Configlet produced at least one warning.
-      These warnings will become errors in a future configlet release (at the end of October 2021).
+      These warnings might become errors in a future configlet release.
       For more information, please see the documentation:""".unindent()
     warn(msg, url, doubleFinalNewline = false)