docs: fix typo in comment of plugin.Plugin.Err()

Signed-off-by: Hsing-Yu (David) Chen <davidhsingyuchen@gmail.com>

plugin/context.go

@@ -80,7 +80,7 @@ type Plugin struct {
 }
 
 // Err returns the errors during initialization.
-// returns nil if not error was encountered
+// returns nil if no error was encountered
 func (p *Plugin) Err() error {
 	return p.err
 }