Please explain the meaning of the text in bold, taken from this Bloomberg article.
Ah, yes. They have shed all gentlemanly reticence over dragging former allies into court.
In this sentence, the term "gentlemanly reticence" would be a normal reluctance amongst gentlemen to do something - in this case: drag their former allies into court.
Dragging ones allies into court would normally not be seen as a particularly moral or proper thing to do, and therefore these gentlemen (who would wish to be seen as moral and proper) would be reluctant to do so.
However, in this case, the gentlemen in question have decided to bring their former allies into court, and so could be said to have "given up their desire to act as gentlemen".
So there we go: to "shed ones gentlemanly reticence to do something" is a formal (and somewhat archaic) way of saying that these gentlemen don't mind sacrificing a bit of their reputation (presumably if it benefits them in someway, which, from the article it seems it will).