Update LICENSE path (#129)

Author: Ali Abdelfattah

ios/instabug_flutter.podspec

@@ -9,7 +9,7 @@ Pod::Spec.new do |s|
 A new flutter plugin project.
                        DESC
   s.homepage         = 'http://example.com'
-  s.license          = { :file => '../LICENSE' }
+  s.license          = { :file => '../LICENSE.md' }
   s.author           = { 'Your Company' => '[email protected]' }
   s.source           = { :path => '.' }
   s.source_files = 'Classes/**/*'