Draft: Fix test to ensure mock behavior is always preserved

What does this MR do and why?

Fix test to ensure mock behavior is always preserved .

Related comment: !98656 (comment 1137130322)

To solove Rubocop role Security/Open, replaced URI.open(GHFM_SPEC_TXT_URI) to URI.parse(GHFM_SPEC_TXT_URI).open in MR(!98656 (merged)).

Original test code:

    allow(URI).to receive(:open).with(ghfm_spec_txt_uri) { ghfm_spec_txt_uri_io }

Replaced test code:

    allow_next_instance_of(URI::HTTP) do |instance|
      allow(instance).to receive(:open).and_return(ghfm_spec_txt_uri_io)
    end

The coverage for the parameter ghfm_spec_txt_uri is missing here.

Fix test to ensure mock behavior is always preserved.

Updated test code:

    allow(URI).to receive(:open).with(ghfm_spec_txt_uri).and_call_original
    allow_next_instance_of(URI::HTTP) do |instance|
      allow(instance).to receive(:open).and_return(ghfm_spec_txt_uri_io)
    end