CI bots are not using the latest pre-release version of Flutter

[elliette]

Context:

The CI bots use the latest version of Flutter that has been rolled into google3. This is determined by looking for the latest Flutter tag that matches X.Y.0-M.0.pre: https://github.com/flutter/devtools/blob/df4df88bc9c22fcc22b65e10ce85312e5b9d1396/tool/latest_flutter_candidate.sh#L11

The latest Flutter rolls into google3 haven't been getting tagged.

• The latest commit to be rolled to google3: https://github.com/flutter/flutter/commit/1c77696615558bf8f9fa7a6e2a473f438f1c03ca
• The latest commit with a pre-release tag (3.23.0-12.0.pre): https://github.com/flutter/flutter/commit/35ae5191402bccbe573bb780c03f832dff0687ed