More linting (#2099)

* Address gocritic findings, enable it

* Enable gosimple, no new findings to address

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"
 	}

doc/util.go

@@ -40,7 +40,7 @@ func hasSeeAlso(cmd *cobra.Command) bool {
 // that do not contain \n.
 func forceMultiLine(s string) string {
 	if len(s) > 60 && !strings.Contains(s, "\n") {
-		s = s + "\n"
+		s += "\n"
 	}
 	return s
 }