The number of contributosr in a QF round isn't calculated correctly

[maryjaf]

As you can see in below pics, base on QF donation table's data, the number of contributor isn't correct

donation table row : 2
Raised from 3 contributors
https://giveth.io/project/end-homelessness-thanks-to-web3-community?tab=donations

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donation table rows : 4 (1 anonymous )
Raised from 6 contributors

https://giveth.io/project/public-nouns-operations?tab=donations

cc: @laurenluz