COPY: secure media -> secure uploads (#24643)

Fixing up the last few holdouts

plugins/chat/spec/validators/chat_allow_uploads_validator_spec.rb

@@ -6,7 +6,7 @@ RSpec.describe Chat::AllowUploadsValidator do
     expect(validator.valid_value?("f")).to eq(true)
   end
 
-  context "when secure media is enabled" do
+  context "when secure uploads is enabled" do
     before do
       SiteSetting.chat_allow_uploads = false
       enable_secure_uploads