chore(deps): update dependency apache-beam to v2.28.0 (#5395)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [apache-beam](https://beam.apache.org) | `==2.27.0` -> `==2.28.0` | [![age](https://badges.renovateapi.com/packages/pypi/apache-beam/2.28.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/pypi/apache-beam/2.28.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/pypi/apache-beam/2.28.0/compatibility-slim/2.27.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/pypi/apache-beam/2.28.0/confidence-slim/2.27.0)](https://docs.renovatebot.com/merge-confidence/) |

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dataflow/encryption-keys/requirements.txt

@@ -1 +1 @@
-apache-beam[gcp]==2.27.0
+apache-beam[gcp]==2.28.0

dataflow/flex-templates/streaming_beam/requirements.txt

@@ -1 +1 @@
-apache-beam[gcp]==2.27.0
+apache-beam[gcp]==2.28.0

dataflow/gpu-workers/requirements.txt

@@ -1,4 +1,4 @@
 Pillow==8.0.1
-apache-beam[gcp]==2.27.0  # Make sure the version matches the apache/beam_python* image tag referenced in the Dockerfile.
+apache-beam[gcp]==2.28.0  # Make sure the version matches the apache/beam_python* image tag referenced in the Dockerfile.
 rasterio==1.2.0
 tensorflow==2.4.0  # Make sure this matches the Dockerfile base image TensorFlow version.

pubsub/streaming-analytics/requirements.txt

@@ -1 +1 @@
-apache-beam[gcp,test]==2.27.0
+apache-beam[gcp,test]==2.28.0