The U.S. Soccer Federation sued the union of its world championship women’s soccer team on Wednesday, saying it fears players may attempt to strike ahead of this year’s Olympics.In a complaint filed in Chicago federal court, the USSF said Richard Nichols, who became executive director of the U.S. Women’s National Soccer Team Players Association in late 2014, has refused to acknowledge a Dec. 31 expiration date contained in a memorandum of understanding agreed to by the governing body and the union in …