ENH Remove old logic to default UTF8 DB setting to 4 bytes

[maxime-rainville]

Description

Remove pointless setting in default project config to update UTF8 setting in DB

Issues

• CMS6: Default to utf8mb4 silverstripe-framework#11336

Related PR

• ENH Default DB settings to use 4 bytes to store UTF8 characters silverstripe-framework#11431
• DOC Add entry about utf8mb4 encoding update to changelog developer-docs#602

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[maxime-rainville]

Build is failing, but it's not clear to me it's got anything to do with this PR.

I've triggered a manual run for the 6 branch and will check later: https://github.com/silverstripe/recipe-core/actions/runs/11417090805

[GuySartorelli]

Some of the failures are unrelated for sure. Some might just be because we're expecting these values for the connection. Rerunning now that the framework PR has been merged.

[GuySartorelli]

This is now only failing in the same places as the 6 branch of the repo itself.
Change looks good. Thanks!