chore(sdk): bump version to 1.8.13

[connor-mccarthy]

Description of your changes:
Bumps version before release. Release is to unblock TFX: #7632 (comment)

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[connor-mccarthy]

/hold

We may want to bump the minor version instead of the patch version to reflect the retry policy feature added by #7875.

[connor-mccarthy]

/wip

[connor-mccarthy]

/remove-wip