fixup!: account for optional leading whitespace

per existing `co-authored-by-is-trailer` rule's regex

Author: JakobJingleheimer

lib/rules/line-length.js

@@ -35,7 +35,7 @@ export default {
       // Skip lines with URLs.
       if (/https?:\/\//.test(line)) { continue }
       // Skip co-authorship.
-      if (/^co-authored-by:/i.test(line)) { continue }
+      if (/^\s*Co-authored-by:/i.test(line)) { continue }
 
       if (line.length > len) {
         failed = true