Revisit diboson njet systematic uncertainty for 1jet category

[abasnet97]

The ttA channels require at least 1 jet as a part of their event selection. However, when we derived the diboson njet uncertainty for Top-22-006, we only derived it for 2+ jet category (cause 2 was the least number of jets in Top-22-006 channels).

In this commit in [1], I have put a temporary placeholder value of 1.0 for the 1jet category, but we will need to revisit this in the future to get a more accurate estimate.

[1] 4696058