Ruby: Error parsing embedded multiline blocks

**Description of the issue**

Seeing this error in the CodeQL run: `A parse error occurred. Check the syntax of the file. If the file is invalid, correct the error or exclude the file from analysis.`

The errored code block in question looks something like this and runs correctly.

```ruby
<<~BLOCKA
if some_condition?
<<~BLOCKB
BLOCKB
end
BLOCKA
```

首先使用 issue 中嵌入的 Ruby 範例重現 CodeQL 解析錯誤，重點關注巢狀的多行區塊。追蹤 Ruby 剖析器對這種類似 heredoc 的語法的處理；當具有此結構的有效程式碼能夠在不出現所回報錯誤的情況下完成剖析時，即表示完成。

由索引模型根據 Issue 內容生成。