Keep terminal check naming convention

terminal_check_appengine.go

@@ -1,4 +1,4 @@
-// +build appengine js
+// +build appengine
 
 package logrus
 

terminal_check_js.go

@@ -6,6 +6,6 @@ import (
 	"io"
 )
 
-func (f *TextFormatter) checkIfTerminal(w io.Writer) bool {
+func checkIfTerminal(w io.Writer) bool {
 	return false
 }