[AIRFLOW-2088] Fix duplicate keys in MySQL to GCS Helper function

[kaxil]

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-2088

Description

• Here are some details about my PR, including screenshots of any UI changes:
• Remove the duplicate key in MySqlToGoogleCloudStorageOperator in the type_map helper function that maps from MySQL fields to BigQuery fields.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:
  Minor change

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
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

• Passes git diff upstream/master -u -- "*.py" | flake8 --diff

[codecov-io]

Codecov Report

Merging #3022 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3022   +/-   ##
=======================================
  Coverage   73.19%   73.19%           
=======================================
  Files         177      177           
  Lines       12415    12415           
=======================================
  Hits         9087     9087           
  Misses       3328     3328

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[Fokko]

Thanks!