chore(deps): update dependency google-cloud-vision to v2.4.0 (#178)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [google-cloud-vision](https://togithub.com/googleapis/python-vision) | `==2.3.2` -> `==2.4.0` | [![age](https://badges.renovateapi.com/packages/pypi/google-cloud-vision/2.4.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/pypi/google-cloud-vision/2.4.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/pypi/google-cloud-vision/2.4.0/compatibility-slim/2.3.2)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/pypi/google-cloud-vision/2.4.0/confidence-slim/2.3.2)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>googleapis/python-vision</summary>

### [`v2.4.0`](https://togithub.com/googleapis/python-vision/blob/master/CHANGELOG.md#&#8203;240-httpswwwgithubcomgoogleapispython-visioncomparev232v240-2021-07-12)

[Compare Source](https://togithub.com/googleapis/python-vision/compare/v2.3.2...v2.4.0)

##### Features

-   add always_use_jwt_access ([#&#8203;166](https://www.github.com/googleapis/python-vision/issues/166)) ([bff7763](https://www.github.com/googleapis/python-vision/commit/bff7763c586284eab96b3f43573006273e2e71ee))

##### Bug Fixes

-   disable always_use_jwt_access ([8cc57cc](https://www.github.com/googleapis/python-vision/commit/8cc57cc21809596737e7a42102510942426ee3e6))
-   disable always_use_jwt_access ([#&#8203;171](https://www.github.com/googleapis/python-vision/issues/171)) ([8cc57cc](https://www.github.com/googleapis/python-vision/commit/8cc57cc21809596737e7a42102510942426ee3e6))

##### Documentation

-   omit mention of Python 2.7 in 'CONTRIBUTING.rst' ([#&#8203;1127](https://www.github.com/googleapis/python-vision/issues/1127)) ([#&#8203;161](https://www.github.com/googleapis/python-vision/issues/161)) ([78740ad](https://www.github.com/googleapis/python-vision/commit/78740ade95bf3eb7a2c613383e6ed602dfd1f1db)), closes [#&#8203;1126](https://www.github.com/googleapis/python-vision/issues/1126)

##### [2.3.2](https://www.github.com/googleapis/python-vision/compare/v2.3.1...v2.3.2) (2021-06-02)

##### Bug Fixes

-   **deps:** add packaging requirement ([#&#8203;147](https://www.github.com/googleapis/python-vision/issues/147)) ([41b88bd](https://www.github.com/googleapis/python-vision/commit/41b88bd482d4d6ec76fc6efc99aa9343496faf72))

##### [2.3.1](https://www.github.com/googleapis/python-vision/compare/v2.3.0...v2.3.1) (2021-04-13)

##### Documentation

-   insert spaces between classes and methods in docs ([#&#8203;133](https://www.github.com/googleapis/python-vision/issues/133)) ([1495241](https://www.github.com/googleapis/python-vision/commit/1495241f7f19098ba33412e5c6f98c76b0bedfb2))

</details>

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vision/snippets/crop_hints/requirements.txt

@@ -1,2 +1,2 @@
-google-cloud-vision==2.3.2
+google-cloud-vision==2.4.0
 pillow==8.3.1

vision/snippets/detect/requirements.txt

@@ -1,2 +1,2 @@
-google-cloud-vision==2.3.2
+google-cloud-vision==2.4.0
 google-cloud-storage==1.41.0

vision/snippets/document_text/requirements.txt

@@ -1,2 +1,2 @@
-google-cloud-vision==2.3.2
+google-cloud-vision==2.4.0
 pillow==8.3.1

vision/snippets/face_detection/requirements.txt

@@ -1,2 +1,2 @@
-google-cloud-vision==2.3.2
+google-cloud-vision==2.4.0
 pillow==8.3.1

vision/snippets/product_search/requirements.txt

@@ -1,2 +1,2 @@
-google-cloud-vision==2.3.2
-google-cloud-storage==1.41.0
+google-cloud-vision==2.4.0
+google-cloud-storage==1.41.0

vision/snippets/quickstart/requirements.txt

@@ -1 +1 @@
-google-cloud-vision==2.3.2
+google-cloud-vision==2.4.0

vision/snippets/web/requirements.txt

@@ -1 +1 @@
-google-cloud-vision==2.3.2
+google-cloud-vision==2.4.0