Address code review comments

- Improve variable name
- Add Changelog
- Remove unnecessary let_it_be

app/presenters/snippet_blob_presenter.rb

@@ -39,8 +39,8 @@ class SnippetBlobPresenter < BlobPresenter
   end
 
   def renderer
-    proxy = Warden::Proxy.new({}, Warden::Manager.new({})).tap do |i|
-      i.set_user(current_user, scope: :user)
+    proxy = Warden::Proxy.new({}, Warden::Manager.new({})).tap do |proxy_instance|
+      proxy_instance.set_user(current_user, scope: :user)
     end
 
     ApplicationController.renderer.new('warden' => proxy)

changelogs/unreleased/al-205505-fix-snippet-blob-viewers.yml

+---
+title: Fix snippet blob viewers for rich and plain data
+merge_request: 25945
+author:
+type: fixed

spec/presenters/snippet_blob_presenter_spec.rb

@@ -4,8 +4,6 @@ require 'spec_helper'
 
 describe SnippetBlobPresenter do
   describe '#rich_data' do
-    let_it_be(:snippet) { create(:personal_snippet) }
-
     before do
       allow_next_instance_of(described_class) do |instance|
         allow(instance).to receive(:current_user).and_return(nil)