[AIRFLOW-5853] BigQuery - standardize task_ids in example_dag

[TobKed]

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[codecov-io]

Codecov Report

Merging #6505 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #6505      +/-   ##
=========================================
+ Coverage   83.69%   83.7%   +<.01%     
=========================================
  Files         635     635              
  Lines       36716   36716              
=========================================
+ Hits        30731   30734       +3     
+ Misses       5985    5982       -3

Impacted Files	Coverage Δ
airflow/gcp/example_dags/example_bigquery.py	100% <ø> (ø)	⬆️
airflow/models/taskinstance.py	93.79% <0%> (+0.5%)	⬆️

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[TobKed]

CC @mik-laj