Venture Global and the bankers helping to take it public hoped to capitalize on President Trump’s pro-oil-and-gas agenda. Instead, the gas exporter met pushback from prospective investors, and slashed its target price by more than one-third Wednesday. When Venture Global launched its initial public offering last week, its goal was to raise up to $2.3 billion by selling 50 million shares at $40 to $46 apiece.