deps: Update dependency mypy to v1.8.0 (#221)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [mypy](https://www.mypy-lang.org/)
([source](https://github.com/python/mypy),
[changelog](https://mypy-lang.blogspot.com/)) | `==1.7.1` -> `==1.8.0` |
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|
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|
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|
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|

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<details>
<summary>python/mypy (mypy)</summary>

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Source](https://github.com/python/mypy/compare/v1.7.1...v1.8.0)

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langchain_tools_demo/requirements-test.txt

@@ -1,6 +1,6 @@
 black==24.1.1
 pytest==8.0.0
-mypy==1.7.1
+mypy==1.8.0
 isort==5.13.2
 types-requests==2.31.0.20240125
-types-python-dateutil==2.8.19.20240106
+types-python-dateutil==2.8.19.20240106

retrieval_service/requirements-test.txt

@@ -2,8 +2,8 @@ asyncpg-stubs==0.29.1
 black==24.1.1
 httpx==0.26.0
 isort==5.13.2
-mypy==1.7.1
 pytest==8.0.0
+mypy==1.8.0
 pytest-asyncio==0.23.4
 types-PyYAML==6.0.12.12
 csv-diff==1.1