Allow "minimum-stability: RC"

[koehnlein]

The current TYPO3 core development requires "doctrine/dbal 4.0.0-RC2@rc" which cannot be installed without explicitly allowing "RC"

Here is the current error message, I ran into.

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - typo3/cms-core[dev-main, 13.1.x-dev] require doctrine/dbal 4.0.0-RC2@rc -> found doctrine/dbal[4.0.0-RC2] but it does not match your minimum-stability.
    - typo3/cms-core 13.1.x-dev is an alias of typo3/cms-core dev-main and thus requires it to be installed too.
    - Root composer.json requires typo3/cms-core @dev -> satisfiable by typo3/cms-core[dev-main, 13.1.x-dev (alias of dev-main)].

[ochorocho]

LGTM, thank you :-)