ignore_external_function_updates is not used

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## Describe the Bug
I was trying to use `ignore_external_function_updates` to set ignore on source changes and foudn that this variable is not used anywhere in the code.

## Expected Behavior
It actually changes behaviour :)

## Steps to Reproduce
* Set to `true` and see nothing changes
*
## Environment (please complete the following information):

Anything that will help us triage the bug will help. Here are some ideas:
- OS: all
- Version 0.4.1

## Additional Context
Add any other context about the problem here.

在 Terraform 模块中搜索 `ignore_external_function_updates` 的声明和引用，然后跟踪将其设置为 `true` 时如何处理源代码更改。复现 0.4.1 版本中报告的行为，并确认该设置会改变是否忽略外部函数更新。

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