[AIRFLOW-5504] Improve project_id in GCP Kubernetes Hook

[TobKed]

Make sure you have checked all steps below.

Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-5504
  • In case you are fixing a typo in the documentation you can prepend your commit with [AIRFLOW-XXX], code changes always need a Jira issue.
  • In case you are proposing a fundamental code change, you need to create an Airflow Improvement Proposal (AIP).
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Description

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Tests

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Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
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Documentation

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[codecov-io]

Codecov Report

Merging #6126 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #6126      +/-   ##
=========================================
- Coverage   80.11%   80.1%   -0.01%     
=========================================
  Files         607     607              
  Lines       34902   34902              
=========================================
- Hits        27961   27959       -2     
- Misses       6941    6943       +2

Impacted Files	Coverage Δ
airflow/gcp/hooks/kubernetes_engine.py	95.89% <100%> (ø)	⬆️
airflow/jobs/local_task_job.py	85% <0%> (-5%)	⬇️
airflow/jobs/scheduler_job.py	74.28% <0%> (-0.31%)	⬇️
airflow/utils/dag_processing.py	58.98% <0%> (+0.18%)	⬆️
airflow/models/taskinstance.py	93.72% <0%> (+0.5%)	⬆️

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