chore(deps): update dependency google-cloud-pubsub to v1.7.0 (#4290)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [google-cloud-pubsub](https://togithub.com/googleapis/python-pubsub) | minor | `==1.6.1` -> `==1.7.0` |

---

### Release Notes

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

### [`v1.7.0`](https://togithub.com/googleapis/python-pubsub/blob/master/CHANGELOG.md#&#8203;170-httpswwwgithubcomgoogleapispython-pubsubcomparev161v170-2020-07-13)

[Compare Source](https://togithub.com/googleapis/python-pubsub/compare/v1.6.1...v1.7.0)

##### New Features

-   Add support for server-side flow control. ([#&#8203;143](https://togithub.com/googleapis/python-pubsub/pull/143)) ([04e261c](https://www.github.com/googleapis/python-pubsub/commit/04e261c602a2919cc75b3efa3dab099fb2cf704c))

##### Dependencies

-   Update samples dependency `google-cloud-pubsub` to `v1.6.1`. ([#&#8203;144](https://togithub.com/googleapis/python-pubsub/pull/144)) ([1cb6746](https://togithub.com/googleapis/python-pubsub/commit/1cb6746b00ebb23dbf1663bae301b32c3fc65a88))

##### Documentation

-   Add pubsub/cloud-client samples from the common samples repo (with commit history). ([#&#8203;151](https://togithub.com/googleapis/python-pubsub/pull/151)) 
-   Add flow control section to publish overview. ([#&#8203;129](https://togithub.com/googleapis/python-pubsub/pull/129)) ([acc19eb](https://www.github.com/googleapis/python-pubsub/commit/acc19eb048eef067d9818ef3e310b165d9c6307e))
-   Add a link to Pub/Sub filtering language public documentation to `pubsub.proto`. ([#&#8203;121](https://togithub.com/googleapis/python-pubsub/pull/121)) ([8802d81](https://www.github.com/googleapis/python-pubsub/commit/8802d8126247f22e26057e68a42f5b5a82dcbf0d))

</details>

---

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appengine/flexible/pubsub/requirements.txt

@@ -1,3 +1,3 @@
 Flask==1.1.2
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0
 gunicorn==20.0.4

appengine/standard_python3/pubsub/requirements.txt

@@ -1,4 +1,4 @@
 Flask==1.1.2
 google-api-python-client==1.9.3
 google-auth==1.19.0
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0

appengine/standard_python37/pubsub/requirements.txt

@@ -1,4 +1,4 @@
 Flask==1.1.2
 google-api-python-client==1.9.3
 google-auth==1.19.0
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0

asset/cloud-client/requirements.txt

@@ -1,5 +1,5 @@
 google-cloud-storage==1.29.0
 google-cloud-asset==1.3.0
 google-cloud-resource-manager==0.30.2
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0
 google-cloud-bigquery==1.25.0

container_registry/container_analysis/requirements.txt

@@ -1,4 +1,4 @@
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0
 google-cloud-containeranalysis==0.3.1
 grafeas==0.4.1
 pytest==5.3.0; python_version > "3.0"

dlp/requirements.txt

@@ -1,5 +1,5 @@
 google-cloud-dlp==1.0.0
 google-cloud-storage==1.29.0
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0
 google-cloud-datastore==1.13.0
 google-cloud-bigquery==1.25.0

functions/ocr/app/requirements.txt

@@ -1,4 +1,4 @@
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0
 google-cloud-storage==1.29.0
 google-cloud-translate==2.0.1
 google-cloud-vision==1.0.0

functions/pubsub/requirements.txt

@@ -1 +1 @@
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0

functions/tips/requirements.txt

@@ -1,5 +1,5 @@
 google-cloud-error-reporting==0.34.0
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0
 python-dateutil==2.8.1
 requests==2.24.0
 xmltodict==0.12.0

healthcare/api-client/dicom/requirements.txt

@@ -1,5 +1,5 @@
 google-api-python-client==1.9.3
 google-auth-httplib2==0.0.4
 google-auth==1.19.0
-google-cloud-pubsub==1.6.1
+google-cloud-pubsub==1.7.0
 requests==2.24.0