Remove custom retry map for exponential retries.

[adamsilverstein]

Bug Description

In #2442 / b1b73c9 we added a custom retry map for exponential retries. The main reason we added this was to avoid retrying for lightouseErrors which can return a 500 code even when not retryable.

Since that time, I opened a PR to add this config to the upstream library which has now been merged: googleapis/google-api-php-client#2010. The client config now matches ours, so we can remove our custom config:

https://github.com/adamsilverstein/google-api-php-client/blob/b4aadd3a71213a19a9076af90a1cbef85eec8a83/src/Task/Runner.php#L75-L86

Steps to reproduce

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Screenshots

Additional Context

• PHP Version:
• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Plugin Version [e.g. 22]
• Device: [e.g. iPhone6]

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Acceptance criteria

• The exponential retry feature should use the default configuration.
• The PHP API client should be running at least version 2.9.0 (when the upstream change was released)

Implementation Brief

• In /includes/Core/Authentication/Clients/OAuth_Client.php:
  • Remove the retry map array.
  • Remove the line setting the retry config: $client->setConfig( 'retry_map', $this->retry_map );
• In composer.json update the version for google/apiclient to the latest released version. (currently 2.9.1).

Test Coverage

• No change.

Visual Regression Changes

• No change.

QA Brief

• Engineer to confirm the retry map has been removed.

Changelog entry

• Update Google API client library and remove custom configuration to retry failed API requests as it is now covered in the library itself.

[felixarntz]

Noting here that we'll need to require at least version 2.9.0 of the google-api-php-client to make this change.

[felixarntz]

@adamsilverstein Can you update the ACs and IB based on the above? Afterwards should be good.

[adamsilverstein]

👍🏼 Updated.

[felixarntz]

IB ✅

[benbowler]

Added a PR and QA:Eng line.

[tofumatt]

QA ✅