Tests: Allow `wpdb::set_sql_mode()` tests to run on MySQL 8.0.11+.

MySQL 8.0.11 removed support for the `NO_AUTO_CREATE_USER` SQL mode, which was used in as an example of a mode compatible with WordPress.

`NO_AUTO_VALUE_ON_ZERO` is now used in the affected tests instead, which is supported on both MySQL 5.7.x and 8.0.x.

Props kaggdesign, jeremyfelt, afragen.
Fixes #44586. See #49344.
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git-svn-id: https://core.svn.wordpress.org/trunk@46983 1a063a9b-81f0-0310-95a4-ce76da25c4cd