commans: Remove unneeded build constraint

Fixes #2886

commands/limit_darwin.go

@@ -11,7 +11,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// +build darwin
 // Copyright 2015 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");