Simplify flutter.rb by removing sha256 checks

Removed platform-specific sha256 checks for macOS and Linux.

Author: izzalDev

Casks/f/flutter.rb

@@ -1,5 +1,6 @@
 cask "flutter" do
   version "3.38.1"
+  sha256 :no_check
 
   url "https://github.com/flutter/flutter.git",
       branch:   "stable",
@@ -8,14 +9,6 @@
   desc "UI toolkit for building applications for mobile, web, and desktop"
   homepage "https://flutter.dev/"
 
-  on_macos do
-    sha256 :no_check
-  end
-
-  on_linux do
-    sha256 :no_check
-  end
-
   livecheck do
     url "https://github.com/flutter/flutter.git"
     regex(/^v?(\d+(?:\.\d+)+)$/i)