Pick the appropriate project code from Forecast if more than one exists

[yongrenjie]

https://github.com/alan-turing-institute/whatwhat/blob/be0c2559c74cd9bdea75b6e4512a3d6b134c9f0a/lib/forecast.ml#L105-L109

choose the one beginning with hut23-, instead of just picking the first one.

[yongrenjie]

These are really finance codes, not the project issue number, so we actually want to search for something of the form CHAR-STR-STR.