fix words misspell

Signed-off-by: Michael Wan <zirenwan@gmail.com>

plugin/plugin.go

@@ -89,7 +89,7 @@ type Registration struct {
 
 	// InitFn is called when initializing a plugin. The registration and
 	// context are passed in. The init function may modify the registration to
-	// add exports, capabilites and platform support declarations.
+	// add exports, capabilities and platform support declarations.
 	InitFn func(*InitContext) (interface{}, error)
 }