feat: Upgrade to cobra v1.8.1

Signed-off-by: John McBride <jpmmcbride@gmail.com>

vendor/github.com/spf13/cobra/doc/man_docs.go

@@ -133,7 +133,7 @@ func fillHeader(header *GenManHeader, name string, disableAutoGen bool) error {
 		}
 		header.Date = &now
 	}
-	header.date = (*header.Date).Format("Jan 2006")
+	header.date = header.Date.Format("Jan 2006")
 	if header.Source == "" && !disableAutoGen {
 		header.Source = "Auto generated by spf13/cobra"
 	}