[AIRFLOW-3396] Make sql param as required in BigQueryOperator

[kaxil]

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[kaxil]

Instead of allowing None and then adding condition, we should remove it.

This was made earlier when we had bql and sql and wanted to deprecate bql

[codecov-io]

Codecov Report

Merging #4224 into master will increase coverage by 1.09%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #4224      +/-   ##
=========================================
+ Coverage    77.8%   78.9%   +1.09%     
=========================================
  Files         201     201              
  Lines       16360   17675    +1315     
=========================================
+ Hits        12729   13946    +1217     
- Misses       3631    3729      +98

Impacted Files	Coverage Δ
airflow/utils/dag_processing.py	56.13% <0%> (-1.4%)	⬇️
airflow/jobs.py	77.36% <0%> (+0.27%)	⬆️
airflow/configuration.py	89.39% <0%> (+0.34%)	⬆️
airflow/models.py	95.14% <0%> (+2.8%)	⬆️

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[bolkedebruin]

@kaxil please use a jira for this, it doesnt qualify as a doc change ;-)

[kaxil]

@bolkedebruin :) Updated.

[kaxil]

ping @Fokko

[ashb]

When did we release the change that deprecated/removed BQL?

The code change is fine, just wondering about upgrade paths for people with by back-compat hat on 🎩

[kaxil]

@ashb We issued deprecation warning in 1.10.0:

https://github.com/apache/incubator-airflow/blob/1.10.0/airflow/contrib/operators/bigquery_operator.py

and we haven't yet removed it in 1.10.1 and don't plan to remove it in 1.10.2 as well.