internal/cocoainit: move app/internal/cocoainit

We're about to move app/headless to gpu/headless, and it imports
cocoainit.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/log/log_ios.go

@@ -17,7 +17,7 @@ import (
 	"log"
 	"unsafe"
 
-	_ "gioui.org/app/internal/cocoainit"
+	_ "gioui.org/internal/cocoainit"
 )
 
 func init() {