Fix: typo

Corrected "eror" to "error" on line 331.

app.go

@@ -328,7 +328,7 @@ func (a *App) RunContext(ctx context.Context, arguments []string) (err error) {
 // RunAndExitOnError calls .Run() and exits non-zero if an error was returned
 //
 // Deprecated: instead you should return an error that fulfills cli.ExitCoder
-// to cli.App.Run. This will cause the application to exit with the given eror
+// to cli.App.Run. This will cause the application to exit with the given error
 // code in the cli.ExitCoder
 func (a *App) RunAndExitOnError() {
 	if err := a.Run(os.Args); err != nil {